Free radically curable dental compositions

ABSTRACT

The present invention relates to novel free-radically curable dental compositions, comprising chain-like and/or cyclic and/or cage-type polysiloxanes substituted by free-radically polymerizable groups and having at least 3 silicon atoms and/or mixed forms thereof, disiloxanes substituted by free-radically polymerizable groups, optionally one, two, three or more free-radically curable dental monomers having no silicon atom, fillers, initiators and/or catalysts for free-radical polymerization, and also further customary additives, to the cured dental products formed from the dental compositions of the invention, and to the respective use thereof as dental material, especially as flowable filling composites (called “flow materials”), core buildup materials and luting cements. The invention further relates to a method for producing the dental compositions and to a process for producing a respective dental product. Additionally claimed are inventive kits containing the novel free-radically curable dental compositions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Patent Application No.102014116389, filed Nov. 11, 2014, which is herein incorporated byreference in its entirety.

BACKGROUND OF THE DISCLOSURE

The present invention relates to novel free-radically curable dentalcompositions, comprising chain-like and/or cyclic and/or cage-typepolysiloxanes substituted by free-radically polymerizable groups andhaving at least 3 silicon atoms and/or mixed forms thereof, disiloxanessubstituted by free-radically polymerizable groups, optionally one, two,three or more free-radically curable dental monomers having no siliconatom, fillers, initiators and/or catalysts for free-radicalpolymerization, and also further customary additives, to the cureddental products formed from the dental compositions of the invention,and to the respective use thereof as dental material, especially asflowable filling composites (called “flow materials”), core buildupmaterials and luting cements. The invention further relates to a processfor producing the dental compositions and to a method for producing arespective dental product. Additionally claimed are inventive kitscontaining the novel free-radically curable dental compositions.

Further aspects of the present invention and preferred configurationsthereof will become apparent from the description which follows, theworking examples and the claims.

Polysiloxane compounds having at least 3 silicon atoms for the purposesof the present text have at least one chain or a plurality of chainshaving alternating and mutually connected silicon atoms and oxygenatoms, wherein the chains are also linked to form rings of differentsize, or to form even more extensive structures such as cages, andwherein organic groups (organic side chains) are bonded to the siliconatoms. These organic groups may be of chemically very differentcomposition and hence lead to a multitude of polysiloxane compoundshaving different properties. Frequently, these organic groups have oneor more organically polymerizable groups (i.e. reactive groups) whichcan react with, for example, one or more organically polymerizablegroups in another polysiloxane compound and hence form crosslinkedpolymerized polysiloxane compounds. Chain, ring and cage structures mayalso occur in the form of mixed structures. They are likewise part ofthe dental compositions of the invention.

Polysiloxane compounds have long been known and are obtainable, forexample, by hydrolysis and condensation of silanes having hydrolyzablegroups (see, for example, DE 27 58 414 A1) or by hydrosilylation ofallyl or vinyl compounds with SiH-containing compounds. Polysiloxanecompounds can be processed further to give a multitude of products, forexample overlayers, coatings, membranes or bulk materials. This furtherprocessing is frequently based on a crosslinking reaction of organicallypolymerizable groups in the polysiloxane compounds (e.g. (meth)acrylategroups) and the resulting formation of crosslinked polysiloxanecompounds.

“(Meth)acryl . . . ” is understood in the context of the present text tomean both “acryl . . . ” and “methacryl . . . ”.

A specific group of polysiloxane compounds contains, in the organicgroups (side chains), besides an organically polymerizable group,additional free polar functional groups, for example hydroxyl orcarboxyl groups.

For instance, DE 44 16 857 C1 relates to hydrolyzable and polymerizablesilanes, to processes for preparation thereof and to the use thereof forproduction of silica (hetero)polycondensates and (hetero)polymers.Hydrolyzable, organically modified silanes find wide use in theproduction of scratch-resistant coatings for a wide variety of differentsubstrates, for the production of fillers, of adhesives and sealingcompounds or of shaped bodies.

DE 44 16 857 C1 discloses the use of silica (hetero)-polycondensates(polysiloxane compounds) in curable dental materials. The polysiloxanecompounds described here comprise free polar functional groups (e.g.carboxyl or hydroxyl groups) capable of complexing suitable metalions/transition metal ions (e.g. ions of titanium, zirconium or tin). Incurable dental compositions, this can have a positive effect on x-rayopacity, on contact toxicity and on the refractive index of acorresponding curable or cured dental material.

DE 198 60 364 C2 relates to polymerizable dental compositions based onsiloxane compounds that are capable of curing, and to the use andproduction thereof. This publication describes the preparation of cyclicpolysiloxanes and the use thereof as a basis for polymerizable dentalcompositions. In spite of high density of groups capable ofpolymerization, they are said to have a low viscosity which enables highfiller loading, which leads to compositions having low polymerizationshrinkage. Here too, free polar functions are present as well as thepolymerizable units in the organic side chains of the polysiloxanesdescribed.

The free polar functional groups, for example in the aforementionedpolysiloxane compounds, however, regularly lead to unwanted propertiestoo. For instance, it has been found that the hydrophilicity of thepolysiloxane compounds caused by the (free) polar functional groupsleads to increased water absorption in the presence of moisture, whichreduces the wet strength of the curable dental material in adisadvantageous manner. Probably due to the formation of internalhydrogen bonds, there is an increase in viscosity. This then has anadverse effect on handling in the production of the curable dentalcompositions.

There is a considerable need on the part of dental practitioners and thedental industry to adapt polysiloxane compounds further to the demandson a modern (curable or cured) dental material and to minimize theaforementioned disadvantages. Polysiloxane compounds adapted in such away should have improved physical properties for dental purposes (i.e.lead to dentally improved physical properties of the correspondingcurable/cured dental materials), for example lower polymerizationshrinkage on polymerization/crosslinking of the polysiloxane compounds(i.e. on curing), increased strength and/or restricted water absorptionwith simultaneously comfortable consistency of the curable dentalmaterial.

The first successes in the improvement of the polysiloxanes wereachieved through addition or substitution of different substrates ontothe free polar functionalities of the above-described specificpolysiloxanes.

EP 1 874 847 B1 relates to a process for preparing silanes having two,three or even more structural units linked together by a urethane-, acidamide- and/or carboxylic ester-containing bridge, each of which containsat least one organically polymerizable radical and at least one silylradical. These silanes should especially be suitable for modification ofthe properties of silicic acid (hetero)polycondensates andsilyl-containing organic polymers. The process disclosed should also besuitable for bridging of already precondensed silicic acid(hetero)polycondensates.

The silicic acid (hetero)polycondensates (polysiloxane compounds)disclosed in EP 1 874 847 B1 have a free hydroxyl group (i.e. a freepolar functional group). These free hydroxyl groups can react with adicarboxylic acid derivative or diisocyanate such that hydroxyl groupsform a link (bridge) with a dicarboxylic acid derivative ordiisocyanate. Such linked polysiloxane compounds have a much highermolecular weight without any significant reduction in the double bonddensity (as a result of the organically polymerizable (meth)acrylategroups). Double bond density is understood here to mean the quotient ofthe number of polymerizable double bonds in a compound and the molecularweight of this compound. The higher molecular weight has a positiveeffect on biocompatibility and polymerization shrinkage on crosslinkingof the linked polysiloxane compounds. At the same time, thehydrophobicity of the polysiloxane compounds was increased. However, ithas been found that the higher molecular weight has an adverse effect onthe viscosity of the linked polysiloxane compounds (and hence onprocessibility in manufacturing the curable dental material). Theviscosity rises markedly with the degree of crosslinking, i.e. with themolecular weight, such that there is no longer satisfactorily tolerableprocessibility in manufacturing a corresponding curable dental materialcomprising such linked polysiloxane compounds, even at quite a lowdegree of linkage.

EP 1 685 182 B1 relates to silanes and silicic acid polycondensates andpartial condensates formed therefrom, in which an organic radical bondedto a silicon is present, which is branched and bears an independentlyorganically polymerizable group at each of the two branches, or bearssuch a group at one of the two branches and has a radical having afurther silicon atom at the other.

The polysiloxane compounds disclosed in EP 1 685 182 B1 also comprisefree polar functional groups in the form of hydroxyl groups. By reactionof carboxylic acid or isocyanate derivatives which themselves likewisecomprise polymerizable double bonds (e.g. (meth)acrylate groups), it isthus possible to link organically polymerizable groups onto free polarfunctional groups. These reaction products regularly have elevatedstrength with simultaneously increased hydrophobicity and improvedbiocompatibility due to the elevated molecular weight.

However, in these cases too, it has been shown that the introduction ofadditional polymerizable double bonds leads to increased polymerizationshrinkage on crosslinking of the polysiloxane compounds, since thedouble bond density is markedly increased, but the increase in themolecular weight is only comparatively small.

WO 2013/041723 A1 discloses hydrolyzable and polymerizable silanes(including silicic acid polycondensates, i.e. siloxanes) havingadjustable spatial distribution of the functional groups, and the usethereof. The teaching disclosed in WO 2013/041723 A1 relates to a methodfor chain extension of radicals bonded to silicon via carbon in silanesor siloxanes.

WO 2013/053693 A1 discloses silicic acid polycondensates (siloxanes)having cyclic olefin-containing structures and methods for preparationthereof, and the use thereof. WO 2013/053693 A1 discloses that polymermaterials having moduli of elasticity adjustable within wide limitscombined with high elastic strain (i.e. without brittleness) and hencehigh fracture toughness can be produced from silicic acid(hetero)polycondensates having cyclic olefin-containing structures.

The as yet unpublished DE 10 2014 210 432 describes polysiloxanecompounds which have the aforementioned disadvantages from the prior artin a curable or cured dental composition at least only in attenuatedform, if at all. The conceptual approach to these systems is based onthe idea of converting the free functional group in the silane such thatno additionally polymerizable double bonds are introduced into thesystem. Instead, hydrocarbyl radicals of high molecular weight having atleast 11 carbon atoms are incorporated into the system. Surprisingfindings in the case of these curable dental compositions were

-   -   a good viscosity of the polysiloxane compounds (the viscosity        should be 50 Pa*s or less at a temperature of 25° C.) and an        associated excellent processibility in the production of a        curable dental material containing the polysiloxane compounds,    -   good hydrophobicity,    -   good strength, especially good flexural strength,    -   very low polymerization shrinkage on crosslinking of the        polysiloxane compounds, i.e. on curing of the curable dental        material,    -   good biocompatibility,    -   a refractive index almost identical to the refractive index of        standard dental glasses.

The measures taken in DE 10 2014 210 432 thus solved several problems atonce:

-   -   Elimination of polar functional groups prevented the formation        of intermolecular interactions. It was thus possible to keep the        viscosity of the system at a comparatively low level in spite of        a remarkable increase in molecular weight.    -   Incorporation of hydrocarbyl radicals of relatively high        molecular weight resulted in widening of intramolecular spacing        in the polysiloxane structure, and so it was possible to        increase the accessibility of the free-radically polymerizable        groups during the curing and hence to optimize the conversion        rate. How else could one explain the fact that in these systems,        with a comparatively reduced double bond density, the strength        of the materials, for example the flexural strength of the cured        dental compositions, remains at a very good level and in many        cases is actually increased compared to the polysiloxanes        without further conversion.    -   The increase in molecular weight with the same functionality,        i.e. in the case of an effective lowering of the double bond        density, made it possible to adjust especially what is perhaps        the clinically most important technical parameter for a curable        dental composition, namely the value of the volume shrinkage        during the curing, to an extremely low value. In clinical        practice, therapeutic success is also dependent primarily on        whether the dental material, for example, seals a cavity        prepared by the dentist with high marginal integrity. As a        result of shrinkage of the material in the course of        polymerization, marginal gaps can form, through which bacteria        penetrate into the tooth and then cause the treatment to fail.    -   Incorporation of hydrocarbyl residues of relatively high        molecular weight also made the polysiloxane structure        comparatively hydrophobic, such that the unwanted absorption of        water now adopts extremely low values.

The free-radically curable compositions described in DE 10 2014 210 432are especially suitable for use in a therapeutic method for temporary orpermanent filling of a dental cavity. The systems are additionallysuitable for use in a therapeutic method as base material, as adhesive(bonding), as a flowable composite material (flow material), as afissure sealant, as a crown and bridge material, as an inlay/onlayand/or as core buildup material.

SUMMARY OF THE DISCLOSURE

In in-house studies, it has now been found that further tremendousimprovements in free-radically curable dental compositions containingpolysiloxanes, specifically both the novel polysiloxanes from DE 10 2014210 432 and the above-described systems from the prior art, are possiblewhen free-radically polymerizable disiloxanes are added thereto. Theseimprovements are manifested particularly when the free-radically curabledental compositions have a “moderate” filler loading as envisaged, forexample, for applications as flowable composite materials (flowmaterials), as core buildup materials or as luting cements, or have a“low” filler loading, as appropriate, for example, for “adhesives”, forfissure sealants or for dental lacquers.

The term “moderate” filler loading corresponds to a percentage of fillerof about 50%-85% by weight, based on the overall composition, whereinthe filler comprises all the different fractions of nano- and microscalefiller.

The term “low” filler loading corresponds to a percentage of filler ofabout 0%-50% by weight, based on the overall composition, wherein thefiller here too comprises all the different fractions of nano- andmicroscale filler.

The abovementioned filler ranges are stated here as guide values andshould be regarded as such, since there are also very specificfree-radically curable dental compositions which use, for example,greater amounts of nanoscale fillers, such that they are used with afiller content of 70% by weight, based on the overall composition, asfissure sealants. These sealing materials could also be used as flowablecomposite materials (flow materials).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the moduli of elasticity of Examples 1-4.

FIG. 2 shows the curves for the viscosity as a function of shear ratefor the inventive flowable material 5-A and for the two comparativematerials 5-B and 5-F.

FIG. 3 shows the curves for the viscosity as a function of shear ratefor the inventive flowable material 5-A and for the three comparativematerials 5-B, 5-D, and 5-E.

DETAILED DESCRIPTION OF THE DISCLOSURE

The improvements achieved are directed primarily to the consistency ofthe free-radically curable dental compositions of the invention.

The consistency of the free-radically curable dental compositions is ofexceptional importance in the case of application of the dental materialto an extremely narrow application tip, for example by means of atwo-chamber mixing cartridge, a compule or a dental syringe, since the(hydrophobic) free-radically curable dental composition must have a goodadaptation to the (hydrophilic) tooth substance, in order to ensuresuccessful tooth treatment. The above-described important properties ofthe polymer, low shrinkage, low water absorption or good mechanicalstrength, will not be realized in tooth treatment unless the dentalcomposition can be applied optimally to the tooth.

On the one hand, the dental material thus must have exceptionalflowability, both on application through a narrow application cannula ora static mixer and on adaptation to the tooth substance. Low-resistanceflow characteristics through the application cannula or the static mixerare required to keep the push-out forces within acceptable limits.Excessively high push-out forces prevent, inter alia, preciseapplication and thus put successful treatment at risk. Optimaladaptation of the dental material to the tooth substance prevents theformation of marginal gaps, and hence prevents the formation ofsecondary caries and hence makes a crucial contribution to the successof the treatment.

On the other hand, the dental material is also to have a certainstability. While still in the syringe, compule or cartridge, asufficiently high stability prevents separation of the material andhence increases its storage stability. In addition, the dental material,as soon as it has been applied to the tooth substance or into the cavityand has adapted in an optimal manner, is again to have a sufficientlyhigh stability in order not to “run” from the tooth or out of thecavity.

This profile of requirements is achieved by intrinsically opposingproperties, for example through the use of rheology-modifying substancessuch as aerosils. Typically, about one to three percent aerosil is usedin order to achieve the desired shear gradient. When the polysiloxanesare used, these amounts of aerosil, however, are insufficient to be ableto establish a sufficient shear gradient. In order to achieve asufficient shear gradient, amounts of aerosil of in some cases tenpercent or more are necessary here. However, these large amounts ofaerosil then cause a distinct drop in the total filler content and hencein the good properties as well, for example the high flexural strengthand low shrinkage. Due to the inventive combination of the polysiloxaneswith disiloxanes, a monomer system in which the customary amounts ofaerosil of one to three percent are already sufficient to bring about asufficient shear gradient, has surprisingly been found. The effect foundappears to be based on the interaction of polysiloxane and disiloxaneand not on mere dilution of the polysiloxane. The mere dilution of thepolysiloxane or the drop in the filler content leads to increasedflowability over the entire range. This means that the material eitherhas inadequate flow characteristics combined with sufficient stability,or that the material has inadequate stability combined with sufficientflow characteristics. In the extreme case, the material even has neitheradequate stability nor adequate flowability.

The inventive combinations of polysiloxanes with disiloxanes are thus ofparticularly good suitability for production of flowable curable dentalmaterials which are applied through an application cannula or a staticmixer, such as flowable composites, core buildup materials or lutingcomposites. As well as good flow properties in the cannula or mixer andoptimal adaptation to the tooth substance, these materials havesufficiently high stability, and the good physical properties introducedby the polysiloxanes can be fully effective.

Furthermore, the combination of polysiloxanes with disiloxanessurprisingly also increases the modulus of elasticity of the cureddental material. The cured material can thus offer greater resistance todeformation and thus better withstand the constant chewing stresses.

The use of disiloxanes in free-radically curable dental compositions,having a chemical structure based on the conventional crosslinking“dental monomers” such as bis-GMA(2,2-bis[p-(2′-hydroxy-3′-methacryloyloxy-propoxy)phenyl]propane), UDMA(1,6-bis(methacryloyloxy-2-ethoxycarbonylamino)-2,4,4-trimethylhexane),TEGDMA (triethylene glycol dimethacrylate), HEDMA (hexanedioldimethacrylate), etc., is known from the prior art.

In a publication entitled “Synthesis and properties of a polyfluorinatedprepolymer multifunctional urethane acrylate” (J. M. Antonucci, J. W.Stansbury, S. Venz, “Polymeric Materials Science and Engineering”, 59,388-396 (1988)), in which what are called “low surface energy resins”are examined, bis(methacryloyloxypropyl)tetramethyldisiloxane(BIS-MPTMS) is used together with triethylene glycol dimethacrylate(TEGDMA) and hexamethylene 1,6-dimethacrylate (HEDMA) as organic resinmatrix in a dental composite composition in the form of a powder/liquidsystem. On page 390, in the paragraph “Formulation of composites”, it isstated that BIS-MPTMS is an excellent agent for reducing viscosity andhas a voluminous flexible structure. It is said to be miscible with manydental resins over a wide concentration range.

In an abstract entitled “Evaluation of siloxane containing dentalcomposites” (J. S. Kuo, J. M. Antonucci, W. Wu, “Journal of DentalResearch Abstracts”, 6A, and Abstract No. 30 (1985)), BIS-MPTMS is usedtogether with bis-GMA and UDMA as organic resin matrix. Here too, it isstated that BIS-MPTMS is miscible with dental base monomers over a widerange (10%-50% by weight). The conclusion of this study reads:“Mechanical properties of the siloxane-containing composites were almostcomparable to the controls, but, significantly, had reduced WS (watersorption) and enhanced OER (oral environmental resistance).”

In a more recent publication entitled “Synthesis of none bisphenol Astructure dimethacrylate monomer and characterization for dentalcomposite applications” (X. Liang, F. Liu, J. He, “Dental Materials”,30, 917-925 (2014)), the reaction product (SiMA) of the ring-openingaddition reaction between1,3-bis[2-(3,4-epoxy-cyclohex-1-yl)ethyl]tetramethyldisiloxane andmethacrylic acid as a bis-GMA alternative was examined together withTEGDMA as organic matrix in dental composites. The authors conclude thatthe “study of SiMA based resin and composite material showed that SiMAhad potential to be used in clinic, but mechanical properties of SiMAbased resin and composite needed to be improved . . . ” (page 923, point5, “conclusion”).

None of the prior art documents regarding free-radically curable dentalcompositions which relate to polysiloxanes or disiloxanes as alternativemonomer units to the conventional dental monomers have—aside from thequestion of the mechanical properties of the cured dental composition,the viscosity during the preparation of the siloxane and of thecorresponding dental composite, the shrinkage characteristics during thepolymerization, the water absorption of the polymer, thebiocompatibility or the refractive indices of the individualconstituents of the curable dental material—concentrated on thefundamental problem of the push-out characteristics and the adaptationto hard tooth substance in the curable dental composition.

According to the invention, the stated object is achieved by afree-radically curable dental compositions comprising

-   -   a.) chain-like and/or cyclic and/or cage-type polysiloxanes        substituted by free-radically polymerizable groups and having at        least 3 silicon atoms and/or mixed forms thereof,    -   b.) disiloxanes substituted by free-radically polymerizable        groups and having the following structure:

R¹ _(a)R² _((3-a))Si—O—SiR² _((3-b))R¹ _(b) with

-   -   -   R²: alkyl, alkenyl, aryl, alkylaryl, arylalkyl, wherein            different R² may be the same or different,        -   R¹: YZ,        -   Z: free-radically polymerizable group selected from the            structural elements —O—(C═O)—CH═CH₂, —O—(C═O)—C(CH₃)═CH₂,            —(C═O)—CH═CH₂, —(C═O)—C(CH₃)═CH₂, —CH═CH₂, —(CH₃)═CH₂,            —NH—(C═O)—CH═CH₂ and —NH—(C═O)—C(CH₃)═CH₂,        -   wherein different Z may be the same or different,        -   a: 1 or 2,        -   b: 1 or 2,        -   Y: a connecting element which links the silicon atom to the            free-radically polymerizable group and consists of an            alkylene group,        -   wherein the alkylene group is an unsubstituted, linear,            straight-chain or branched hydrocarbyl chain or        -   wherein the alkylene group is an unsubstituted hydrocarbyl            group interrupted by a urethane group, urea group, ester            group, thiourethane group or amide group or        -   wherein the alkylene group is a hydrocarbyl group            substituted by a hydroxyl group and/or this hydroxyl group            has been esterified or etherified or wherein the alkylene            group is a hydrocarbyl group interrupted by an oxygen atom            and/or nitrogen atom and/or sulfur atom and/or ester groups            and/or thioester groups and substituted by a hydroxyl group            and/or this hydroxyl group has been esterified or etherified            and        -   wherein different Y may be the same or different and        -   wherein Y contains 20 or fewer carbon atoms and        -   wherein YZ is chosen such that Z always has a maximum number            of atoms,

    -   c.) optionally one, two, three or more free-radically curable        monomers having no silicon atom,

    -   d.) 85 percent by weight or less of fillers based on the total        weight of the free-radically curable dental composition,

    -   e.) initiators and/or catalysts for the free-radical        polymerization and

    -   f.) further customary additives.

A preferred composition of the invention is a dental compositionfree-radically curable in a chemical and/or light-induced manner.

A very particularly preferred composition of the invention is afree-radically curable dental composition, wherein the polysiloxanes(a.) are obtained by hydrolysis or partial hydrolysis and subsequentcondensation or co-condensation of one, two, three or more compounds R¹_(a)R² _(b)SiX_(c) with

-   -   X: halogen or alkoxy,    -   R²: alkyl, alkenyl, aryl, alkylaryl, arylalkyl, wherein        different R² may be the same or different,    -   R¹: YZ,    -   Z: free-radically polymerizable group selected from the        structural elements —O—(C═O)—CH═CH₂, —O—(C═O)—C(CH₃)═CH₂,        —(C═O)—CH═CH₂, —(C═O)—C(CH₃)═CH₂, —CH═CH₂, —C(CH₃)═CH₂,        —NH—(C═O)—CH═CH₂ and —NH—(C═O)—C(CH₃)═CH₂,    -   wherein different Z may be the same or different,    -   a: 1 or 2,    -   b: 0 or 1,    -   c: 2 or 3,

a+b+c=4,

-   -   Y: a connecting element which links the silicon atom to the        free-radically polymerizable group and consists of an alkylene        group,    -   wherein the alkylene group is an unsubstituted, linear,        straight-chain or branched hydrocarbyl chain or    -   wherein the alkylene group is an unsubstituted hydrocarbyl group        interrupted by a urethane group, urea group, ester group,        thiourethane group or amide group or    -   wherein the alkylene group is a hydrocarbyl group substituted by        a hydroxyl group or this hydroxyl group has been esterified or        etherified or    -   wherein the alkylene group is a hydrocarbyl group interrupted by        an oxygen atom and/or nitrogen atom and/or sulfur atom and/or        ester groups and/or thioester groups and substituted by a        hydroxyl group or this hydroxyl group has been esterified or        etherified and    -   wherein different Y may be the same or different and    -   wherein Y contains 20 or fewer carbon atoms and    -   where YZ is chosen such that Z always has a maximum number of        atoms.

Constituent a—chain-like and/or cyclic and/or cage-type polysiloxanessubstituted by free-radically polymerizable groups and having at least 3silicon atoms and/or mixed forms thereof.

Chain-like and/or cyclic and/or cage-type polysiloxanes substituted byfree-radically polymerizable groups and having at least 3 silicon atomsand/or mixed forms thereof can be synthesized via the sol-gel process bycontrolled hydrolysis and condensation of appropriately functionalizedderivatives of alkoxides of silicon or of halosilanes. These productionmethods have been described many times in the literature. In general,such a synthesis proceeds from a standard silane, for exampleisocyanatopropyldiethoxysilane, which is reacted in a first step,likewise in a standard reaction, for example in an isocyanate-alcoholpolyaddition, for example with glycerol 1,3-dimethacrylate, to give thecorresponding urethane. The compound obtained here consists on the onehand of the silicon atom which is furnished with hydrolyzable andcondensable groups and is linked via a spacer consisting of an alkylgroup (here a propyl group) and a urethane group as structuralconnecting element to a further functional structural segment, in thiscase to two free-radically polymerizable methacrylate groups. Such asimple synthesis method can be modified in various ways, since thepossible reactions between appropriately functionalized silanes andsuitable reactants seem unlimited. There is a correspondingly largenumber of synthesis suggestions in the literature. The starting compoundthus comprises an inorganically condensable structural element, avariable connecting element and a free-radically crosslinkable organicbase structure. In a catalytically controlled hydrolysis andcondensation, the polysiloxane is obtained as an inorganic condensatesubstituted by free-radically polymerizable groups. Whether thepolycondensate is in the form of chains, rings or three-dimensional cageforms, or in the corresponding mixed forms, depends on the exactconditions of the condensation. These include not only the reactionconditions (pH, amount of solvent and water, type and amount ofcatalyst, reaction temperature, manner of processing, etc.) but also thestructural forms of the starting silane, important factors being thenumber of alkoxy groups, the number of free-radically polymerizablegroups, the chemical nature of the connecting element and the chainlength of the spacer. Details of this can be found both in thescientific literature and in the patent literature.

The polysiloxanes, being a link between inorganic and organic chemistry,have exceptional material properties. Since they are additionallyphysiologically inert, i.e. have no significant toxicity, they areespecially important for applications in medicine. The reason whypolysiloxanes are virtually nontoxic is the low biological attackabilityof the silicon-carbon bonds and the restricted ability of the highlyhydrophobic polymer chains to diffuse through cell membranes, which iswhy they should be particularly suitable for implantation (in teeth).

Constituent b—disiloxanes substituted by free-radically polymerizablegroups and having the following structure:

R¹ _(a)R² _((3-a)) Si—O—SiR² _((3-b))R¹ _(b) withR²: alkyl, alkenyl, aryl, alkylaryl, arylalkyl, wherein different R² maybe the same or different,

R¹: YZ,

Z: free-radically polymerizable group selected from the structuralelements —O—(C═O)—CH═CH₂, —O—(C═O)—C(CH₃)═CH₂, —(C═O)—CH═CH₂,—(C═O)—C(CH₃)═CH₂, —CH═CH₂, —C(CH₃)═CH₂, —NH—(C═O)—CH═CH₂ and—NH—(C═O)—C(CH₃)═CH₂,wherein different Z may be the same or different,a: 1 or 2,b: 1 or 2,Y: a connecting element which links the silicon atom to thefree-radically polymerizable group and consists of an alkylene group,wherein the alkylene group is an unsubstituted, linear, straight-chainor branched hydrocarbyl chain orwherein the alkylene group is an unsubstituted hydrocarbyl groupinterrupted by a urethane group, urea group, ester group, thiourethanegroup or amide group orwherein the alkylene group is a hydrocarbyl group substituted by ahydroxyl group and/or this hydroxyl group has been esterified oretherified orwherein the alkylene group is a hydrocarbyl group interrupted by anoxygen atom and/or nitrogen atom and/or sulfur atom and/or ester groupsand/or thioester groups and substituted by a hydroxyl group and/or thishydroxyl group has been esterified or etherified andwherein different Y may be the same or different andwherein Y contains 20 or fewer carbon atoms and wherein YZ is chosensuch that Z always has a maximum number of atoms.

Disiloxanes are characterized by exceptional chain mobility, since thecompounds have free rotation about the silicon-oxygen bonds, one reasonfor which is the difference in size between the oxygen atom and thesilicon atom. This leads to compounds having a remarkable low viscositybecause of the flexibility of the structure thereof. In addition, theshielding of the oxygen atoms by the hydrocarbyl groups on the siliconleads to marked hydrophobicity and to greatly restricted interaction ofthe chains with one another, such that spreading on surfaces, forexample on hard tooth substance, should be favored and should result inextremely good adaptation of the polysiloxanes, for example to preparedcavity walls.

As well as some commercially available inventive disiloxanes (e.g.1,3-bis(3-methacryloyloxypropyl)-tetramethyldisiloxane,1,3-bis(3-methacryloyloxy-2-hydroxypropoxypropyl)tetramethyldisiloxane,1,3-bis-[(acryloyloxymethyl)phenethyl]tetramethyldisiloxane), there arenumerous synthesis strategies for preparation of the inventivedisiloxanes.

1,3-Bis(3-methacryloyloxy-2-hydroxypropoxypropyl)disiloxane 6 can beprepared by reaction of the corresponding1,3-bis(3-glycidoxypropyl)disiloxane 5 with methacrylic acid.

The disiloxane 8 can be synthesized from1,3-bis(3-glycidoxypropyl)disiloxane 5 by reaction with ethanol and thenmethacrylic anhydride.

It is possible to prepare the corresponding disiloxanes 9, 10, 11, 12and 13 from 1,3-bis(3-methacryloyloxy-2-hydroxypropoxypropyl)disiloxane6 by further reaction with different acid chlorides or anhydrides.

It is also possible to synthesize the corresponding disiloxane 14 from1,3-bis(3-glycidoxypropyl)disiloxane 5 by reaction withmono(2-methacryloyloxyethyl) succinate.

The corresponding urea derivative 16 is obtained from commerciallyavailable 1,3-bis(3-aminopropyl)disiloxane 15 by reaction with2-isocyanatoethyl methacrylate.

It is possible to prepare the corresponding disiloxanes 17 and 18 from1,3-bis(3-aminopropyl)disiloxane 15 by reaction with, respectively, 2and 4 equivalents of glycidyl methacrylate.

1,3-Bis(3-methacrylamidopropyl)disiloxane 19 is likewise obtainable from1,3-bis(3-aminopropyl)-disiloxane 15 by reaction with methacryloylchloride.

The corresponding urethane derivative 21 is obtained from commerciallyavailable 1,3-bis(3-hydroxypropyl)-disiloxane 20 by reaction with2-isocyanatoethyl methacrylate.

The corresponding1,3-bis(3-methacryloyloxy-2-hydroxy-propoxypropyl)disiloxane 6 is alsoobtainable in turn from 1,3-bis(3-hydroxypropyl)disiloxane 20 byreaction with glycidyl methacrylate.

The corresponding 1,3-bis(3-methacryloyloxypropyl)-disiloxane 22 islikewise obtained from 1,3-bis(3-hydroxypropyl)disiloxane 20 by reactionwith methacryloyl chloride.

The corresponding thiourethane derivative 24 is obtained fromcommercially available 1,3-bis(3-mercaptopropyl)disiloxane 23 byreaction with 2-isocyanatoethyl methacrylate.

The corresponding disiloxane 25 is obtainable from1,3-bis(3-mercaptopropyl)disiloxane 23 by reaction with glycidylmethacrylate.

The corresponding amide derivative 27 is obtained from commerciallyavailable 1,3-bis(3-carboxypropyl)-disiloxane 26 by reaction with2-isocyanatoethyl methacrylate.

The corresponding disiloxane 28 is also obtainable from1,3-bis(3-carboxypropyl)disiloxane 26 by reaction with glycidylmethacrylate.

Of course, a multitude of (meth)acryloyl-substituted disiloxanesproceeding from the dichlorodisiloxanes are also obtainable via typicalsilane chemistry. Mention is made here by way of example of the reactionwith lithium aluminum hydride to give the dihydrodisiloxane andsubsequent platinum-catalyzed reaction with allyl methacrylate to givethe corresponding 1,3-bis(3-methacryloyloxypropyl)disiloxane 22.

Of course, the inventive disiloxanes are not just obtainable byfunctionalization of disiloxanes, but can also be prepared proceedingfrom monoalkoxysilanes by hydrolysis and condensation. For example, theunsymmetric disiloxanes 32 are also obtainable by reaction of differentmonoalkoxysilanes 31a/b. For the functionalization of themonoalkoxysilanes, conceivable functionalization reactions include thosealready described for the disiloxanes.

Constituent c—optionally one, two, three or more free-radically curablemonomers having no silicon atom

The free-radically curable monomers having no Si atom are monomers whichare substances having preferably one, two or more ethylenic groups, forexample but not restricted to the (meth)acrylate monomers customarilyused in dental chemistry.

The (meth)acrylate monomers may be monofunctional or elsepolyfunctional.

Monofunctional (meth)acrylate monomers used with preference are theesters of (meth)acrylic acid with alkyl groups of 1 to 12 carbon atomsand esters of (meth)acrylic acid containing aromatic groups having 6 to12 carbon atoms, wherein the alkyl groups and aromatic groups that formthe esters may contain substituents such as hydroxyl groups and etherbonds.

The patent literature mentions a multitude of further compounds (forexample in DE 39 41 629 A1, which is incorporated in the presentapplication by way of reference), all of which are esters of acrylic ormethacrylic acid and are suitable for use in a curable mixture.

The free-radically polymerizable monomers may also be hydroxyl compoundshaving at least one ethylenic double bond. In this case, it is possiblewith preference to use the hydroxyl compounds of (meth)acrylatescustomarily used in dental chemistry.

Examples of polyfunctional (meth)acrylate monomers also includedi(meth)acrylates of alkylene glycol having 2 to 20 carbon atoms,di(meth)acrylates of oligomers of alkylene glycol, polyalkylene glycoldi(meth)acrylate, di(meth)acrylates of bisphenol A or of the diglycidylether of bisphenol A.

Particular preference is further given to free-radically curablecompounds based on a central polyalicyclic structural element, forexample3(4),8(9)-bis((meth)acryloyloxymethyl)tricyclo[5.2.1.0^(2,6)]decane,alkoxylated3(4),8(9)-bis((meth)acryloyl-oxymethyl)tricyclo[5.2.1.0^(2,6)]decane,2,3-bis((meth)-acryloyloxymethyl)bicyclo[2.2.1]heptane, alkoxylated2,3-bis((meth)acryloyloxymethyl)bicyclo[2.2.1]heptane,1,3,5-tri(meth)acryloyloxytricyclo[3.3.1.1^(3,7)]decane, alkoxylatedtri(meth)acryloyloxytricyclo[3.3.1.1^(3,7)]-decane, and (meth)acrylatesof tricyclo[5.2.1.0^(2,6)]-decane-3(4),8(9)-dimethanol, alkoxylatedtricyclo-[5.2.1.0^(2,6)]decane-3(4),8(9)-dimethanol,bicyclo[2.2.1]-heptane-2,3-dimethanol, alkoxylatedbicyclo[2.2.1]-heptane-2,3-dimethanol, 1,3,5-adamantanetriol,alkoxylated 1,3,5-adamantanetriol, with urethane, urea, amide,allophanate, acylurea or biuret groups arranged between thepolyalicyclic structural element and the (meth)acrylates.

Details of the preparation of these substituted (meth)acrylates can befound in patent applications EP 11 183 333, EP 11 183 328, EP 11 183345, EP 11 183 338, EP 11 183 342 and EP 11 188 086, and in thepublications cited in these documents. These citations are likewiseincorporated into the present application by way of reference.

Preference is likewise given to urethane (meth)acrylates, reactionproducts formed from 2 mol of a (meth)acrylate with a hydroxyl group andone mole of a diisocyanate.

In a preferred curable mixture of the invention, constituent (c)contains one or more (meth)acrylate monomers chosen from the groupconsisting of3(4),8(9)-bis((meth)acryloyloxymethyl)tricyclo[5.2.1.0^(2,6)]decane,alkoxylated3(4),8(9)-bis((meth)acryloyloxy-methyl)tricyclo[5.2.1.0^(2,6)]decane,2,3-bis((meth)acryl-oyloxymethyl)bicyclo[2.2.1]heptane, alkoxylated2,3-bis((meth)acryloyloxymethyl)bicyclo[2.2.1]heptane,1,3,5-tri(meth)acryloyloxytricyclo[3.3.1.1^(3,7)]decane, alkoxylatedtri(meth)acryloyloxytricyclo[3.3.1.1^(3,7)]-decane, (meth)acrylates oftricyclo[5.2.1.0^(2,6)]decane-3(4),8(9)-dimethanol, alkoxylatedtricyclo[5.2.1.0^(2,6)]-decane-3(4),8(9)-dimethanol,bicyclo[2.2.1]heptane-2,3-dimethanol, alkoxylatedbicyclo[2.2.1]heptane-2,3-dimethanol, 1,3,5-adamantanetriol, alkoxylated1,3,5-adamantanetriol, with urethane, urea, amide, allophanate, acylureaor biuret groups arranged between the polyalicyclic structural elementand the (meth)acrylates, ethylene glycol di(meth)acrylate,hexane-1,6-diol di(meth)acrylate (HEDMA), triethylene glycoldi(meth)acrylate (TEGDMA), dodecane-1,12-diol di(meth)acrylate,bisphenol A di(meth)acrylate, alkoxylated bisphenol A di(meth)acrylate,bisphenol B di(meth)acrylate, alkoxylated bisphenol B di(meth)acrylate,bisphenol C di(meth)acrylate, alkoxylated bisphenol C di(meth)acrylate,bisphenol F di(meth)acrylate, alkoxylated bisphenol F di(meth)acrylate,polyethylene glycol di(meth)acrylate,7,7,9-trimethyl-4,13-dioxo-5,12-diazahexadecane1,16-dioxydi(meth)acrylate(UDMA), butanediol di(meth)acrylate, tetraethylene glycoldi(meth)acrylate, neopentyl glycol di(meth)acrylate, 2-hydroxypropyl1,3-di(meth)acrylate, 3-hydroxypropyl 1,2-di(meth)acrylate,pentaerythritol di(meth)acrylate, di(meth)acrylates ofdihydroxymethyltricyclo[5.2.1.0^(2,6)]decane, 2-hydroxy-ethyl(meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl(meth)acrylate, 1,2-dihydroxypropyl (meth)acrylate, 1,3-dihydroxypropyl(meth)acrylate,2,2-bis[4-(3-(meth)acryloyloxy-2-hydroxypropoxy]phenyl]propane(bis-GMA), trimethylolpropane tri(meth)acrylate, trimethylolethanetri(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolmethanetri(meth)acrylate, pentaerythritol tetra(meth)acrylate,dimethylolpropane tetra(meth)acrylate, pentaerythritolhexa(meth)acrylate, butylene glycol di(meth)acrylate, propylene glycoldi(meth)acrylate, nonanediol di(meth)acrylate, decanedioldi(meth)acrylate, glycerol mono(meth)acrylate, glyceroldi(meth)acrylate, trimethylolpropane mono(meth)acrylate,trimethylol-propane di(meth)acrylate, sorbitol mono-, di-, tri-, tetra-or penta(meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate,propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate,tetrahydro-furfuryl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl(meth)acrylate, allyl (meth)acrylate, glycidyl (meth)acrylate,2-ethoxyethyl (meth)acrylate, methoxy polyethylene glycol(meth)acrylate, isobornyl (meth)acrylate, 2-(N,N-dimethylamino)ethyl(meth)acrylate, N-methylol(meth)acrylamide, diacetone-(meth)acrylamide,2,2-bis[4-(meth)acryloyloxyphenyl]-propane,2,2-bis[4-(meth)acryloyloxyethoxyphenyl]-propane,2,2-bis[4-(meth)acryloyloxydiethoxyphenyl]-propane,2,2-bis[4-(meth)acryloyloxytriethoxyphenyl]-propane,2,2-bis[4-(meth)acryloyloxytetraethoxyphenyl]-propane,2,2-bis[4-(meth)acryloyloxypentaethoxyphenyl]-propane,2,2-bis[4-(meth)acryloyloxydipropoxyphenyl]-propane,2-[4-(meth)acryloyloxyethoxyphenyl]-2-[4-(meth)acryloyloxy-diethoxyphenyl]propane,2-[4-(meth)-acryloyloxydiethoxyphenyl]-2-[4-(meth)acryloyloxytriethoxyphenyl]propane,2-[4-(meth)acryloyloxydipropoxyphenyl]-2-[4-(meth)acryloyloxytriethoxyphenyl]propane,2,2-bis[4-(meth)acryloyloxyisopropoxyphenyl]propane, neopentyl glycolhydroxypivalate di(meth)acrylate, aceto-acetatoxyethyl (meth)acrylate,polypropylene glycol di(meth)acrylate, glycerol alkoxylatedimethacrylate, neopentyl glycol (meth)acrylate,N,N-(1,2-dihydroxyethylene)bisacrylamide,2,2-bis[4-(meth)acryloyloxypentaethoxyphenyl]propane,2,2-bis[4-(meth)acryloyloxypolyethoxyphenyl]propane, diethylene glycoldi(meth)acrylate, dipentaerythritol tetra(meth)acrylate,dipentaerythritol hexa(meth)-acrylate,N,N-(2,2,4-trimethylhexamethylene)bis[2-(aminocarboxy)-propane-1,3-diol]tetra(meth)acrylate,the condensation product of3-(4)(meth)acryloyloxymethyl-8(9)-hydroxymethyltricyclo[5.2.1.0^(2,6)]decanewith dicarboxylic acids, 2-ethylhexyl (meth)acrylate, tridecyl(meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate, dicyclopentenyl (meth)acrylate, phenyl(meth)acrylate, pentaerythritol mono(meth)acrylate, dipentaerythritolmono(meth)-acrylate, caprolactone-modified tetrahydrofurfuryl(meth)acrylate.

Constituent d—Fillers

A free-radically curable dental composition of the invention contains aproportion of filler particles of 85% by weight or less, preferably of78% by weight or less, based on the total mass of the dental compositionof the invention.

As constituent (d), it is possible to use organic and/or inorganicfillers.

Organic filler particles comprise or consist of, for example, one ormore compounds selected from the group consisting of polyvinyl acetateand copolymers of polyvinyl acetate with one or more polymerizablecompounds, polystyrene, polyethylene, polypropylene, waxes such aspolyethylene wax, polybutylene, polybutadiene, copolymers of butadieneand styrene, polyacrylonitrile, resins such as rosin or hydrocarbonresins, poly(meth)acrylate esters, i.e. reaction products ofpoly(meth)acrylic acid with linear or branched aliphatic, aromatic orcycloaliphatic alcohols such as methanol, ethanol, propanol,isopropanol, the isomeric butanols and higher homologs of the alcoholsmentioned having up to 22 carbon atoms, cyclohexanol, benzyl alcohol andthe like, polydialkyl maleates such as dibutyl maleate and copolymersthereof, and polymers containing silyl groups, such as polyvinylsilanesor copolymers of vinylsilane with one or more of the monomers mentioned.The organic fillers can be used alone or as mixtures.

The inorganic fillers can likewise be used alone or as mixtures. Tooptimize the product properties, the inorganic fillers can be introducedinto the formulations in different particle sizes. The fillers may havea unimodal or polymodal distribution, for example a bimodaldistribution.

As inorganic fillers, it is possible to use compact glasses anddifferent silicas in various sizes and states (monodisperse,polydisperse).

Suitable inorganic constituents are, for example, amorphous materialsbased on mixed oxides composed of SiO₂, ZrO₂ and/or TiO₂, and alsofillers such as quartz glass ceramic or glass powders, barium silicateglasses, barium fluorosilicate glasses, strontium silicate glasses,strontium borosilicate, Li/Al silicate glasses, barium glasses, calciumsilicates, sodium aluminosilicates, fluoroaluminosilicate glasses,oxides of aluminum or silicon, zeolites, apatite, zirconium silicates,sparingly soluble metal salts such as barium sulfate or calciumchloride, and x-ray-opaque fillers such as ytterbium fluoride.

For better incorporation into the polymer matrix, the fillers may beorganically surface-modified. One example is the surface treatment ofthe fillers with a silane. A particularly suitable adhesion promoter ismethacryloyloxypropyltrimethoxysilane.

To adjust the rheology, the free-radically curable dental compositionsmay contain different silicas, preferably fumed silicas.

Preferably, the curable compositions of the invention contain nanoscalesolid particles. The nanoscale solid particles are particles having anaverage particle size of not more than 200 nm, preferably not more than100 nm and especially not more than 70 nm. The nanoscale inorganic solidparticles are preferably those of oxides, sulfides, selenides andtellurides of metals, semimetals and mixtures thereof. Particularpreference is given to nanoscale particles of SiO₂, TiO₂, ZrO₂, ZnO,SnO₂ and Al₂O₂, and mixtures thereof. The nanoscale solid particles areproduced in a known manner, for example by flame pyrolysis, plasmamethods, gas phase condensation, colloid techniques, precipitationmethods, sol-gel methods, etc.

In a preferred configuration, the nanoscale particles are innonagglomerated and/or nonaggregated form, for example dispersed in amedium, preferably in monodisperse form.

In order to enable good binding of the nanoparticles into the polymermatrix of a free-radically curable dental composition of the invention,the surfaces of the nanoparticles have likewise been organicallysurface-modified, meaning that their surfaces have organic structuralelements. Examples include the surface treatment of the fillers with asilane. A particularly suitable adhesion promoter here too ismethacryloyloxypropyltrimethoxysilane.

In a further preferred configuration, the nanoscale particles are thusnonagglomerated and/or nonaggregated, organically surface-modifiednanoparticles having an average particle size of less than 200 nm,preferably less than 100 nm, more preferably less than 70 nm, which havein turn preferably been silanized.

Commercially available nanoscale, nonagglomerated and nonaggregatedsilica sols which can be used in accordance with the invention aretraded, for example, under the “NALCO COLLOIDAL SILICAS” (Nalco ChemicalCo.), “Ludox colloidal silica” (Grace) or “Highlink OG” (Clariant)names.

In a preferred configuration, the filler fraction of a free-radicallycurable dental composition of the invention comprises a mixture of afirst filler (d1) in the form of nonagglomerated, nonaggregatedorganically surface-modified nanoparticles having an average particlesize of less than 200 nm and a second filler (d2) in the form ofmicroparticles having an average particle size in the range from 0.4 μmto 10 μm. The combination of (d1) nanoparticles and (d2) microparticlesin a free-radically curable dental composition of the invention achievescomplete and homogeneous filling of volume of the composite material.This reduces both the shrinkage of the free-radically curablecomposition in the course of curing of the polymer matrix and thesensitivity of the composition of the invention to abrasion.

The proportion of organically surface-modified nanoparticles in apreferred free-radically curable dental composition of the inventionhaving an average particle size of less than 200 nm is greater than 1%by weight, preferably greater than 2% by weight and more preferablygreater than 3% by weight. In in-house studies, it has been found that,in the case of a content of 1% by weight or less of nonagglomeratedand/or nonaggregated organically surface-modified nanoparticles havingan average particle size of less than 200 nm, the free-radically curabledental composition no longer has a sufficient abrasion resistance ineach individual case. One reason for this is probably that, in the caseof a content of 1% by weight or less of said nanoparticles, the regionsbetween the microparticles having an average particle size of 0.4 μm to10 μm are no longer filled adequately. On the other hand, it has beenshown that, in the case of a content of more than 20% by weight ofnonagglomerated and/or -aggregated, organically surface-modifiednanoparticles having an average particle size of less than 200 nm,processibility of the composition is no longer adequate. Because of thehigh solids content, its viscosity then becomes too high.

The materials for the nanoparticles for use in accordance with theinvention are preferably oxides or mixed oxides and are preferablyselected from the group consisting of oxides and mixed oxides of theelements silicon, titanium, yttrium, strontium, barium, zirconium,hafnium, niobium, tantalum, tungsten, bismuth, molybdenum, tin, zinc,ytterbium, lanthanum, cerium, aluminum and mixtures thereof. Thepreferred oxidic nanoparticles are, as explained, nonagglomerated and/ornonaggregated, and have been organically surface-treated.

Within a free-radically curable dental composition of the invention, themicroparticles bring about substantially homogeneous filling of volume,with the remaining cavities between the microparticles at least partlyfilled by the above-described nanoparticles (component (d1)). Inconnection with the present invention, microparticles are understood tomean particles having an average particle size of 400 nm to 10 μm.Preferably, the average particle size is less than 5 μm. It has beenfound that the completeness and homogeneity of the filling of volume ofthe free-radically curable dental composition which is alreadyachievable with the microparticles increases with decreasingmicroparticle size.

The microparticles of component (d2) may have a monomodal or polymodalparticle size distribution, for example a bimodal particle sizedistribution. Microparticles having a bimodal or multimodal particlesize distribution are preferable in accordance with the invention, sincemore complete filling of volume is achievable therewith than in the caseof general use of microparticles having monomodal particle sizedistribution. In the presence of a bi- or multimodal particle sizedistribution, the particles of the fractions having the larger particlesize bring about coarse filling of volume, while the particles of thefraction having the smaller particle size, as far as possible, fill theregions between the particles of the fractions having the largerparticle size. The cavities still remaining are filled by nanoparticlesas described above.

Most preferably, therefore, in a free-radically curable dentalcomposition of the invention, a component (d2) containing two or morefractions of microparticles, with different average particle sizes ofthe fractions, is used.

Preferably, component (d2) contains at least two microparticle fractionswherein the average particle sizes differ from one another by at least0.5 μm, preferably by at least 0.7 μm. In some configurations, thedifference between the average particle sizes of the microparticlefractions is at least 1.0 μm.

The microparticles of different fractions may consist of the samematerial or of different materials; it is also possible for there to betwo or more fractions of microparticles having average particle sizesthat are approximately the same or within a particular range, in whichcase the materials of the particles differ between the fractions.

More preferably, a free-radically curable dental composition of theinvention comprises a component (d2) having one or more firstmicroparticle fractions each having an average particle size in therange from 1 μm to 10 μm, preferably 1 μm to 5 μm, and one or moresecond microparticle fractions each having an average particle size inthe range from >0.4 μm to <1 μm (i.e. larger than 0.4 μm but smallerthan 1 μm), preferably 0.5 μm to 0.8 μm.

Preferably, the ratio of the total mass of the first microparticlefractions to the total mass of the second microparticle fractions is inthe range from 1:1 to 12:1, preferably in the range from 1.5:1 to 8:1.

Preferably, the ratio of the average particle size of the or a firstmicroparticle fraction to the average particle size of the or a secondmicroparticle fraction of component (d2) is in the range from 1.5:1 to10:1, preferably in the range from 2:1 to 5:1.

In a particularly preferred free-radically curable dental composition ofthe invention, component (d2) comprises one or more first microparticlefractions each having an average particle size in the range from 1 μm to10 μm, preferably 1 μm to 5 μm, and one or more second microparticlefractions each having an average particle size in the range from >0.4 μmto <1 μm, preferably 0.5 μm to 0.8 μm; wherein the ratio of the totalmass of the first microparticle fractions to the total mass of thesecond microparticle fractions is in the range from 1:1 to 12:1,preferably 1.5:1 to 8:1 and/or the ratio of the average particle size ofthe or a first microparticle fraction to the average particle size ofthe or a second microparticle fraction of component (d2) is in the rangefrom 1.5:1 to 10:1, preferably 2:1 to 5:1.

In a particularly preferred free-radically curable dental composition ofthe invention, at least a portion of the microparticles of component(d2) is formed by organically surface-modified particles, preferablysilanized particles, and/or at least a portion of the microparticles ofcomponent (d2) is formed by dental glass particles; preferably, at leasta portion of the microparticles of component (d2) is formed byorganically surface-modified dental glass particles, preferablysilanized dental glass particles.

In these cases, component (d2) preferably features a bi- or multimodalparticle size distribution, especially a bi- or multimodal particle sizedistribution having the preferred features described above.

As well as components (d1) and (d2), the free-radically curable dentalcomposition may comprise further fillers as component (d3) in additionto the mixture of filler particles.

For example, it is possible to use reinforcing filler materials such asglass fibers, polyamide fibers or carbon fibers. A free-radicallycurable dental composition of the invention may also contain finesplinter or bead polymers, wherein the bead polymers may be homo- orcopolymers of organically curable monomers.

In a particularly preferred embodiment, a free-radically curable dentalcomposition of the invention contains an x-ray-opaque filler. Mostpreferably, the composition of the invention contains nanoscale YbF₃and/or BaSO₄.

Qualitative and quantitative characterization of the filler particles:

The steps described hereinafter in the qualitative and quantitativecharacterization of the filler particles (especially of nanoscale fillerparticles) are well known to those skilled in the art and are describedcomprehensively in the literature.

Resin/Filler Separation:

In a first step, 1 g of a free-radically curable dental composition ofthe invention (also called composite material hereinafter) isresuspended in 10 mL of acetone and the resultant suspension is thencentrifuged with a centrifuge at 5000 rpm for 10 min. The supernatant(called resin phase hereinafter) is decanted off into a collectionbottle and the residue is slurried in 5 mL of acetone. The mixture iscentrifuged again at 5000 rpm for 10 min and decanted, and the residueis slurried again in 5 mL of acetone. The steps of centrifuge, decantingand slurrying are repeated twice more under identical conditions. Thetotal amount of residues separated from the resin phases is dried, andthe total amount of resin phases is freed of acetone on a rotaryevaporator.

After conducting the first step, the dried total amount of residuesregularly includes those filler particles having a particle size ofabout 400 nm or greater than 400 nm (called macroscopic filler particleshereinafter). The total amount of resin phases freed of acetone (calledresin fraction hereinafter) regularly also includes, as well aspolymerizable monomers, filler particles having a particle size of about400 nm or especially less than 400 nm (called nanoscale particleshereinafter). This method therefore ensures that the dental compositematerial, by centrifugation, is separated completely into (i) a fractionof macroscopic filler particles, especially with regard to the dentalglasses having a size in the order of magnitude of greater than 400 nmup to the high micrometer range, and (ii) a resin fraction includingnanoscale particles.

The median particle size d₅₀ of the macroscopic filler particles for usein accordance with the invention in the filler component (d2) of acomposition of the invention is determined by means of light scattering(laser diffraction), preferably with a Beckman Coulter LS 13320 particlesize analyzer.

The nanoscale particles present in the resin fraction may, for example,be both nonaggregated and/or nonagglomerated particles, for exampleincluding x-ray-opaque particles, for example YbF₃ or BaSO₄, havingparticle sizes within a range from about 3 nm to 200 nm, preferably from5 nm to 200 nm, more preferably from 7 nm to 100 nm and most preferablyfrom 7 nm to 70 nm, and non-x-ray-opaque silicas which take the form,for example, of fumed silicas in the form of aggregates and/oragglomerates having a particle size within a range from about 150 nm toabout 300 nm, or else silicas which are synthesized by the sol-gelprocess (or else from waterglass) and which are likewise innonaggregated and/or nonagglomerated form and have particle sizes withina range from about 3 nm to 200 nm, preferably from 5 nm to 200 nm, morepreferably from 7 nm to 100 mm and most preferably from 7 nm to 70 nm.

The total proportion by mass of inorganic particles in the resinfraction is determined gravimetrically by difference weighing afterasking of an appropriate resin fraction.

TEM in Combination with EELS:

In a second step, the filler particles in the resin fraction aresubjected to a qualitative and quantitative characterization. For thispurpose, TEM (transmission electron microscopy) is used in conjunctionwith EELS (electron energy loss spectroscopy).

By means of TEM, the particle sizes of the individual particles and thenumber thereof are determined; elemental determination of individualparticles is effected by means of EELS.

To conduct the combined TEM/EELS characterization, in a first step, theconcentration of the nanoscale particles in the resin fraction is firstreduced by dilution with curable resin. This very substantially rulesout observation of “overlapping” of nanoscale particles in the laterimages. Such “overlapping” would distort the particle characterization.In-house studies have shown that the optimal particle concentration(i.e. the proportion by volume of the filler particles) for such studiesis 1% by volume, based on the total mass of the diluted sample.

In a second step, bar specimens are produced by curing the diluted resinfractions obtained by dilution with curable resin. These bar specimensare then used to produce several ultrathin sections of thickness 300 nmwith an ultra-diamond knife (for example ULTRACUT UCT, LEICA, Wetzlar).The ultrathin sections are transferred to copper TEM grids forstabilization. This results in thin section preparations. These thinsection preparations are then analyzed with acceleration voltage 120 kVin a TEM with bright field images.

A TEM analysis of the above-described thin section preparations allowsdistinction of nonaggregated and nonagglomerated nanoscale particlesfrom aggregated and/or agglomerated particles (e.g. silicas, for exampleAerosils) (for identification of the chemical composition see thedetails which follow).

If high-resolution images are to be examined, ultrathin sections havinglayer thicknesses of less than 100 nm can be produced and examined.

In a third step, the filler particles in the ultrathin sections or thinsection preparations are chemically characterized by means of EELS pointanalyses, such that the chemical composition of individual particlesbecomes known (for determination of the surface modification ofparticles see the points below).

The volume- or weight-based proportions of particle fractions (includinga plurality thereof if appropriate) are determined in a fourth step froma TEM image as follows: the image section from a TEM image viewed undera microscope is an area having edge lengths a and b which can bedetermined by means of the legend. Multiplying by the thickness c of theultrathin section gives a total volume V_(total) for the area underconsideration in the TEM. This total volume V_(total) is the sum totalof the resin volume V_(resin) and the volume of all the particlesV_(particles) within this volume (the volume of all the particles mayinclude several groups of particles, for example sorted by variouscriteria, for example size). The following equation holds:

V _(total) =a*b*c=V _(resin) +V _(particles).

The volume of individual particles (and hence the volume of all theparticles in the volume under consideration) can be obtained bycalculation via the sphere volume of the individual particles. For thispurpose, in the TEM image, the diameter or radius of an appropriateparticle is determined. The sphere volume calculated therefrom,multiplied by the density of the corresponding material of which theparticle consists (material identifiable by means of EELS), gives themass of the particle. The resin volume, obtainable from the total volumeminus the particle volume, multiplied by the resin density, gives theresin mass. The resin density is obtained very substantially from thedensity of the resin used for dilution and, if appropriate, the densityof the diluted resin fraction (the latter can possibly be neglected inthe calculation of the resin density if the proportion of the dilutedresin is negligible). The proportion of the particles (or a group ofparticles) in percent by weight is calculated fromm_(p)*100/(m_(particles)+m_(resin)) where m_(p) is the mass of theparticle fraction under consideration in the volume under consideration,m_(particles) is the mass of all the particles in the volume in questionand m_(resin) is the mass of the resin in the volume underconsideration. In the final calculation of the proportion by weight ofthe particle fraction under consideration, the dilution factor is takeninto account appropriately.

Determination of Organic Surface Modifications: Preliminary Assessment:

Many known x-ray-opaque filler materials (for example ytterbium fluorideor barium sulfate) have the disadvantage that they can be incorporatedonly with difficulty into the matrix (resin matrix) composed ofpolymerizable monomers (called the organic resin phase) because they donot enter into sufficient chemical bonds (binding options) with thehydrophobic groups of the medium. Vitreous fillers can be incorporatedin an excellent manner into the resin matrix of dental compositematerials, for example, with the aid of silanization via Si—OH groups.In the case of ytterbium fluoride and barium sulfate, no such groups arepresent on the surfaces; they are therefore not silanizable and lead toinadequate physical and chemical resistance in a cured dental material(see WO 2005/011621 A1, bottom of page 2).

The x-ray-opaque nanoscale particles used in a curable dental materialof the invention therefore will not have any silanes on their surfaces.Instead, the linking is effected via nitrogen, oxygen, sulfur and/orphosphorus atoms (again see WO 2005/011621 A1 and our remarks further upin the text).

Removal of Polymerizable Monomers from Nanoscale Particles:

“Cross-Flow” Method:

The removal of polymerizable monomers from nanoscale particles iseffected, for example, in a “cross-flow” method known to those skilledin the art by means of ultrafiltration membranes.

In this method, a resin fraction comprising nanoscale particles,polymerizable monomers and optionally a suitable diluent is pumped froma vessel by means of a pump into a circuit composed of particularmembranes, and the polymerizable monomers pass through the pores of themembranes and are separated as filtrate, while the nanoscale particlesremain within the circuit (and hence within the vessel).

An example of a suitable system for this separating step is the“Vivaflow 50” system from “Sartorius Stedim Biotech GmbH, Göttingen”.The pump drive (7554-95) and pump head come from the “Masterflex L/S”series from “Cole-Parmer Instrument Co.”, Illinois, USA. The operationof the pump is set to 2.5 bar during the filtration. Two separationmembranes of the “50,000 MWCO (PES)” type are connected in series. TheMWCO (molecular weight cutoff) defines the separation limit here, i.e.the size of the molecules which can still pass efficiently through themembrane. This value is reported in daltons. The fractions obtained aresubsequently analyzed as described below.

Sedimentation Field-Flow Fractionation (SF3):

Even better than the “cross-flow” method is the conduction of asedimentation field-flow fractionation (SF3). This can especiallyseparate different particle fractions from one another and additionallyfrom the resin fraction. It is a prerequisite here that the differentparticle fractions differ sufficiently from one another in terms of sizeand/or density.

Corresponding equipment containing a separation column necessary for thepurpose is obtainable from Postnova Analytics GmbH, Landsberg. Themodule containing the separation column is identified as CF2000Centrifugal FFF and is supplemented by the further modules PN7140(Eluent Organizer), PN1130 (Isocratic Pump), PN5300 (Autosampler),PN3621 MALS (21-Multi-Angle Light Scattering Detector) and PN8050(Fraction Collector). In this combination, the Centrifugal FFF systemallows not just the analytical but also the preparative separation ofparticle fractions. The fractions obtained are subsequently analyzed asdescribed below.

Characterization of the Surface Modification:

A sample which has been produced as above and then freed of solvents,containing nanoscale particles in the form of a powder, is subsequentlyexamined by means of spectroscopic methods (for example by means of 1HNMR, 13C NMR, 15N NMR, 29Si NMR and 31P NMR, and also IR).

Signals which cannot be attributed to a silane, for example thegamma-methacryloyloxypropylsilyl radical, are attributed to organicsurface modifications not based on silanes, for example surfacemodifications by means of organic compounds on surfaces of ytterbiumfluoride or barium sulfate particles.

The proportions of organically surface-modified particles and/ornon-organically surface-modified particles can also be determinedregularly by evaluation of the intensities of corresponding vibrationbands in the IR spectrum. For this purpose, reference vibration bands(reference curves) of organically surface-modified or non-organicallysurface-modified particles with the corresponding chemical compositionsare employed.

Characterization by Means of Image Analysis and Raman Spectroscopy:

The person skilled in the art is aware of additional methods and coupledmethods which allow qualitative and quantitative characterization of thefiller particles. In this respect, reference is made, for example, tothe article “Chemische Identität einzelner Partikel” [Chemical Identityof Individual Particles] by Deborah Huck-Jones and Renate Hessemann in“Nachrichten aus der Chemie”, Volume 62, September 2014, pages 886 and887. The combination of image analysis and Raman spectroscopy disclosedtherein is regularly also suitable for characterization of the fillerparticles in the context of the present invention. This is especiallytrue of samples which are obtained by the resin/filler separationdescribed above. An example of a suitable image analysis is again theTEM analysis described in the text above.

Constituent e—Initiators and/or Catalysts for the Free-RadicalPolymerization

A free-radically curable dental composition of the invention ispreferably light-curable and/or chemically curable. Preference is givento a free-radically curable dental composition of the invention, whereinconstituent (e) comprises or consists of one or more light-curinginitiators and/or one or more initiators for chemical curing.

Preferred free-radically curable dental compositions of the inventionare light-curable (photocurable) and comprise light-curing initiators.Examples of a light-curing initiator include substances having onlyphotosensitizing action and combinations of sensitizer and accelerator.

Examples of photosensitizers are alpha-diketones, benzoin alkyl ethers,thioxanthones, benzophenones, acylphosphine oxides, acylgermaniumcompounds, acetophenones, ketals, titanocenes, sensitizing dyes, etc.The sensitizers can be employed alone or in combination. Specificsubstance examples from different classes can be found, for example, inDE 10 2006 019 092 A1, or in DE 39 41 629 C2, which are incorporatedinto the present application by way of reference.

Examples of accelerators which are used together with the sensitizersare tertiary amines, secondary amines, barbiturate acids, tin compounds,aldehydes and sulfur compounds. Specific substance examples fromdifferent classes can be found, for example, in DE 10 2006 019 092 A1 orin DE 39 41 629 C2, which are incorporated into the present applicationby way of reference.

Further suitable initiators and initiator combinations are described inDE 601 16 142, which is incorporated into the present application by wayof reference.

The photoinitiators usable in the context of the present invention arecharacterized in that they can bring about the curing of afree-radically curable dental composition of the invention throughabsorption of light in the wavelength range from 300 nm to 700 nm,preferably from 350 nm to 600 nm and more preferably from 380 nm to 500nm, optionally in combination with one or more coinitiators.

The absorption maximum of camphorquinone (CQ) is about 470 nm and istherefore within the blue light range. Camphorquinone (CQ) is one of thePI₂ initiators and is regularly used together with a coinitiator.

Preferably, a composite material of the invention contains thecombination of an alpha-diketone and an aromatic tertiary amine,preference being given to the combination of camphorquinone (CQ) andethyl p-N,N-dimethylaminobenzoate (DABE).

Likewise preferable is the further combination of the“alpha-diketone/aromatic tertiary amine” system with a phosphine oxide,especially with phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide and/or2,4,6-trimethylbenzoyldiphenylphosphine oxide. With regard to thestructures of suitable phosphine oxides for use in a free-radicallycurable dental composition of the invention, reference is made topublications DE 38 01 511 C2, DE 10 2006 050 153 A1, EP 0 184 095 B1, DE42 31 579 C2, EP 0 366 977 B1, U.S. Pat. No. 7,081,485 B2, DE 32 36 026A1, US 2007/0027229 A1, EP 0 262 629 B1, EP 0 073 413, U.S. Pat. No.7,148,382 B2, U.S. Pat. No. 5,761,169, DE 197 08 294 A1, EP 0 057 474,EP 0 047 902 A, EP 0 007 508, DE 600 29 481 T2, EP 0 980 682 B1, EP 0948 955 B1, EP 1 236 459 B1 and EP 0 173 567 A2, which are incorporatedinto the present application by way of reference.

The phosphine oxides specified in these publications are suitableespecially alone or in combination with the “alpha-diketone/amine”system as photo-polymerization initiator system in a free-radicallycurable dental composition of the invention.

EP 1 905 415 describes polymerizable dental compositions comprisingacylgermanium compounds as initiators.

Alternatively, it is also possible to use borate salts, as described,for example, in U.S. Pat. No. 4,772,530, U.S. Pat. No. 4,954,414, U.S.Pat. No. 4,874,450, U.S. Pat. No. 5,055,372 and U.S. Pat. No. 5,057,393,as photoinitiators, which are incorporated into the present applicationby way of reference.

Further suitable photoinitiators are described in J.-P. Fouassier,Photoinitiation, Photopolymerization and Photocuring, Hanser Publishers,Munich, Vienna, New York 1995, and in J. F. Rabek (ed.), RadiationCuring in Polymer Science and Technology, Vol. II, Elsevier AppliedScience, London, New York 1993, which are incorporated into the presentapplication by way of reference.

The person skilled in the art is aware of various initiators forchemical curing. In this regard, reference is made by way of example toEP 1 720 506. Initiators for chemical curing are also described in thepublications DE 10 2006 019 092 already mentioned above and in DE 39 41629.

Preferred initiators for chemical curing are benzoyl peroxide, lauroylperoxide, especially dibenzoyl peroxide, in combination with amines suchas N,N-dimethyl-p-toluidine, N,N-dihydroxyethyl-p-toluidine, andstructurally related amines.

The peroxides and the amines are divided between two differentcomponents of the dental material. When the amine-containing component(called the base paste) is mixed with the peroxide-containing component(called the initiator or catalyst paste), the reaction of amine andperoxide (redox reaction) initiates the free-radical reaction.

Dual-curing systems comprise a combination of photoinitiators andinitiators for chemical curing.

For example, the base paste may additionally comprise a photoinitiator,such that the base paste can be used either solely as a light-curingdental composition or, together with the initiator paste, as a light-and self-curing dental composition.

As well as the oxidatively active organic peroxide compounds, the redoxsystems used may also be barbituric acids or barbituric acid derivativesand malonylsulfamides.

Among the barbituric acid systems, the “Bredereck systems” are of highimportance. Examples of suitable “Bredereck systems” and references tothe corresponding patent literature can be found in EP 1 839 640 and inDE 1 495 520, WO 02/092021 or in WO 02/092023, which form part of thepresent application by way of reference.

Rather than the barbituric acids, it is also possible to use saltsthereof. Examples of these can be found in the following documents: EP 1872 767, EP 2 070 506, EP 1 881 010, DE 10 2007 050 763, U.S. Pat. No.6,288,138, DE 11 2006 001 049, U.S. Pat. No. 7,214,726 and EP 2 070 935.

Suitable malonylsulfamides are described in EP 0 059 451, which formspart of the present application by way of reference. Preferred compoundsin this context are 2,6-dimethyl-4-isobutylmalonylsulfamide,2,6-diisobutyl-4-propylmalonylsulfamide,2,6-dibutyl-4-propylmalonylsulfamide,2,6-dimethyl-4-ethylmalonylsulfamide and2,6-dioctyl-4-isobutylmalonylsulfamide.

In addition, it is possible to use sulfur compounds in the +2 or +4oxidation state, such as sodium benzenesulfinate or sodiumpara-toluenesulfinate.

To accelerate the curing, the polymerization can be performed in thepresence of heavy metal compounds such as Ce, Fe, Cu, Mn, Co, Sn or Zn,particular preference being given to copper compounds. The heavy metalcompounds are preferably used in the form of soluble organic compounds.Preferred copper compounds here are copper benzoate, copper acetate,copper ethylhexanoate, copper di(methacrylate), copper acetylacetonateand copper naphthenate.

Constituent f—Further Customary Additives

A free-radically curable dental composition of the invention comprisesone or more further additive(s) in some cases.

These additives may have various functions. Customary additives for usein dental materials are known to those skilled in the art; he or shewill select the suitable additive(s) according to the desired function.Typical additives and their functions are described by way of examplehereinafter.

Free-radically light-curable dental compositions as preferred inaccordance with the invention preferably contain one or moreinhibitor(s), also called stabilizer(s). These are typically added inorder to prevent spontaneous polymerization. They react with freeradicals formed prematurely, which are scavenged, prevent prematurepolymerization and increase the storage stability of the light-curabledental composition. Standard inhibitors are phenol derivatives such ashydroquinone monomethyl ether (HQME) or 2,6-di-tert-butyl-4-methylphenol(BHT). Further inhibitors such as tert-butylhydroxyanisole (BHA),2,2-diphenyl-1-picrylhydrazyl radicals, galvinoxyl radicals,triphenylmethyl radicals, 2,3,6,6-tetramethylpiperidinyl-1-oxyl radicals(TEMPO), and derivatives of TEMPO or phenothiazine and derivatives ofthis compound are described in EP 0 783 880 B1, which is incorporatedinto the present application by way of reference. Alternative inhibitorsare specified in DE 101 19 831 A1 or in EP 1 563 821 A1, which areincorporated into the present application by way of reference.

A free-radically curable dental composition preferred in accordance withthe invention thus comprises, as additive, one or more polymerizationinhibitors for increasing the storage stability of the composition,preferably selected from the group consisting of hydroquinone monomethylether (HQME), phenols, preferably 2,6-di-tert-butyl-4-methylphenol (BHT)and tert-butylhydroxyanisole (BHA), 2,2-diphenyl-1-picrylhydrazylradicals, galvinoxyl radicals, triphenylmethyl radicals,2,3,6,6-tetramethylpiperidinyl-1-oxyl radical (TEMPO) and derivativesthereof, and phenothiazine and derivatives thereof.

A free-radically curable composition of the invention may comprise, asadditive, one or more fluoride-releasing substances, preferably sodiumfluoride and/or amine fluorides.

UV absorbers which are capable of absorbing UV radiation, for example,by their conjugated double bond systems and aromatic rings are in somecases part of a free-radically curable dental composition of theinvention. Examples of UV absorbers are2-hydroxy-4-methoxy-benzophenone, phenyl salicylate,3-(2′-hydroxy-5′-methylphenyl)benzotriazole or diethyl2,5-dihydroxy-terephthalate.

Since the teeth should be restored as naturally as possible, it isnecessary to provide dental compositions of the invention in a widevariety of different shades. For this purpose, generally inorganic dyesand organic pigments are utilized in very small amounts, which are thusused as an additive in preferred configurations.

Further optional additives are aromas, dental medicaments, organicpolymers and oligomers, preferably plasticizers, microbicides,preferably bactericides, interface-active substances, preferablysurfactants, preservatives or molecular weight regulators.

A preferred inventive composition comprises the components in thefollowing contents:

-   -   a. 10%-35% by weight, preferably 15%-25% by weight,    -   b. 2%-25% by weight, preferably 5%-15% by weight,    -   c. 0%-20% by weight, preferably 0%-10% by weight,    -   d. 50%-85% by weight, preferably 60%-78% by weight,    -   e. 0.001%-5% by weight, preferably 0.1%-2% by weight and    -   f. 0.001%-20% by weight, preferably 0.001%-10% by weight,        wherein the respective percentages by weight are based on the        total mass of the composition.

In particularly preferred cases, a free-radically curable dentalcomposition of the invention does not contain any constituent c.

In particularly preferred cases, a free-radically curable dentalcomposition of the invention comprises1,3-bis(3-methacryloyloxypropyl)tetramethyldisiloxane as constituent b.

In a very particularly preferred case, a free-radically curable dentalcomposition of the invention does not contain any constituent c andcontains 1,3-bis(3-methacryloyloxypropyl)tetramethyldisiloxane asconstituent b.

The present invention also relates to the free-radically cured dentalcomposition obtainable from the free-radically curable dentalcomposition of the invention by means of free-radical polymerization ofthe polysiloxane compound(s) and the disiloxane compound(s) present inthe composition, and optionally of further polymerizable constituentspresent in the dental material. The polymerization or crosslinking iseffected by means of the organically polymerizable double bonds presentin the (meth)acrylate groups.

The statements made above with regard to preferred embodiments offree-radically curable dental compositions of the invention applycorrespondingly to the free-radically cured dental compositions of theinvention.

The present invention likewise relates to a free-radically curabledental composition of the invention or to a dental compositionfree-radically cured in accordance with the invention for use in atherapeutic method as flowable composite material (flow material), asluting cement and/or as core buildup material.

In-house studies have shown that the free-radically curable dentalcompositions of the invention and the free-radically cured compositionsof the invention lead to excellent results in the aforementionedspecific applications.

The present invention also relates to a method for producing afree-radically curable dental composition, comprising the followingsteps:

-   -   providing constituents a, b, c, d, e, f and    -   mixing the constituents.

The present invention additionally also relates to a method forproducing a free-radically cured dental composition, comprising thefollowing steps:

-   -   providing constituents a, b, c, d, e, f,    -   mixing the constituents and    -   curing the mixture.

In methods of the invention for producing a free-radically curabledental composition polymerizable by means of radiative curing,preference is given to the production of a one-component system. In thiscase, the curable composition contains all the constituents required forlight curing in a single component, and curing is initiated byirradiation with light of a defined wavelength.

Preferably, the one-component system is used as part of a kit of theinvention. The present invention thus also relates to a kit comprising

-   -   one, two or more than two light-curing one-component dental        materials of the invention in a flow syringe and/or compule,    -   optionally one, two or more than two adhesives,    -   optionally one, two or more than two etching gels,    -   optionally one or more than one shade guide,    -   optionally one or more than one brush.

In methods of the invention for production of a free-radically curabledental composition curable (a) by means of light curing and by means ofchemical curing (dual-curing) or (b) only by means of chemical curing,preference is given to the production of a multicomponent system.Curable dental compositions curable by means of chemical curing aregenerally formulated as two-component systems, such that the substancesthat trigger polymerization and the polymerizable compounds are presentin separate components and curing is not effected until the separatedcomponents are mixed. Since dual-curing systems are always alsochemically curing, these compositions are likewise formulated andproduced in two-component form.

Preferably, the two-component system is used as part of a kit of theinvention. The present invention thus also relates to a kit to form acore buildup material, comprising

-   -   core buildup material of the invention in a 2-component syringe    -   static mixer (for mixing of the two components)    -   a plunger or dispenser (for application of the core buildup        material through the static mixer)    -   optionally a compatible adhesive    -   optionally one or more root posts    -   optionally molding aids and/or templates    -   optionally further accessories (brush, drill, etc.).

The present invention therefore also relates to a kit to form a lutingmaterial, comprising

-   -   luting material of the invention in a 2-component syringe    -   static mixer (for mixing of the two components)    -   a plunger or dispenser (for application of the luting material        through the static mixer)    -   optionally a compatible adhesive    -   optionally further adhesion promoters (for example for ceramic        or metal, etc.)    -   optionally try-in pastes    -   optionally further accessories (brush, etc.).

EXAMPLES Substances Used

-   Polysiloxane I: Methacryl-POSS (MA0735, Hybrid Plastics Inc.)-   Polysiloxane II: condensation product of    3-methacryloyloxypropyldimethoxymethylsilane-   Polysiloxane III: condensation product of    3-methacryloyloxypropyltrimethoxysilane-   Polysiloxane IV: condensation product of    3-[(2-hydroxy-3-methacryloyloxy)-propoxy]propyldimethoxymethylsilane-   Disiloxane I: 1,3-bis(3-methacryloyloxy-propyl)tetramethyldisiloxane-   Disiloxane II:    1,3-bis[3-[(2-hydroxy-3-meth-acryloyloxy)propoxy]propyl]tetramethyldisiloxane-   Bis-GMA:    2,2-bis[4-(2-hydroxy-3-meth-acryloyloxypropoxy)phenyl]propane-   TEGDMA: triethylene glycol dimethacrylate-   MDP: 10-methacryloyloxydecyl phosphate-   CQ: DL-camphorquinone-   DABE: ethyl 4-dimethylaminobenzoate-   BHT: 2,6-di(tert-butyl)hydroxytoluene-   DEPT: N,N-bis(2-hydroxyethyl)-p-toluidine-   NTPB: sodium tetraphenylborate-   BPO: dibenzoyl peroxide

Synthesis of the Polysiloxanes Synthesis of Polysiloxane II

100 g (0.42 mol) of 3-methacryloyloxypropyldimethoxymethylsilane aredissolved in 400 mL of ethyl acetate. 10 mL of 1N HCl solution are addeddropwise and the mixture is stirred at 30° C. for 72 h. The mixture isextracted by shaking with 2N NaOH solution, and the organic phase iswashed with water and dried over magnesium sulfate. After addition ofBHT, the mixture is first concentrated by rotary evaporation at 40° C.and then solvent residues (e.g. water and alcohol residues) are drawnoff under reduced pressure by means of an oil pump, in order to removethe alcohol and water residues. This results in a fluid resin having aviscosity of 3 Pa*s at 25° C.

n_(D) ²⁰=1.466

Synthesis of Polysiloxane III

100 g (0.40 mol) of 3-methacryloyloxypropyltrimethoxy-methylsilane aredissolved in 400 mL of ethyl acetate. 15 mL of 1N HCl solution are addeddropwise and the mixture is stirred at 30° C. for 72 h. The mixture isextracted by shaking with 2N NaOH solution, and the organic phase iswashed with water and dried over magnesium sulfate. After addition ofBHT, the mixture is first concentrated by rotary evaporation at 40° C.and then solvent residues (e.g. water and alcohol residues) are drawnoff under reduced pressure by means of an oil pump, in order to removethe alcohol and water residues. This results in a fluid resin having aviscosity of 20 Pa*s at 25° C.

n_(D) ²⁰=1.479

Synthesis of Polysiloxane IV

a) Synthesis of a monomeric silane unit (cf. EP 1 685 182 B1, ex. 3):

Added dropwise to an initial charge of 100 g (0.402 mol) of3-glycidyloxypropyldiethoxymethylsilane under a dry atmosphere are anaddition catalyst, BHT as stabilizer and then 38.05 g (0.442 mol) ofmethacrylic acid, and the mixture is stirred at about 80° C. (about 24h). The conversion is monitored via the decrease in the carboxylic acidconcentration by means of acid titration, and the epoxide conversion bymeans of Raman spectroscopy/epoxide titration. The band characteristicof the epoxide group is detected in the Raman spectrum at 1256 cm⁻¹. Theepoxide and carboxylic acid conversions are 99% and 88% respectively(consequence of the carboxylic acid excess).

b) Hydrolysis or condensation of the monomeric silane unit to give apolysiloxane compound (cf. EP 1 685 182 B1, ex. 6):

After addition of ethyl acetate (1000 mL/mol of monomeric silane unit)and water for hydrolysis with HCl as catalyst to the monomeric silaneunit synthesized, the mixture is stirred at 30° C. The progress of thehydrolysis is monitored by water titration. After stirring at 30° C. forseveral days, the workup is effected by repeatedly extractive shakingwith aqueous NaOH, followed by extractive shaking with water andfiltration through a hydrophobized filter. After addition of BHT, themixture is first concentrated by rotary evaporation at 40° C. and thensolvent residues (e.g. water and alcohol residues) are drawn off underreduced pressure by means of an oil pump, in order to remove the alcoholand water residues. This results in a fluid resin having a viscosity of4.5 Pa*s at 25° C.

n_(D) ²⁰=1.483

Synthesis of the Disiloxanes Synthesis of Disiloxane II

Added dropwise to an initial charge of 100 g (0.28 mol) of1,3-bis(glycidoxypropyl)disiloxane under a dry atmosphere are anaddition catalyst, BHT as stabilizer and then 26.10 g (0.30 mol) ofmethacrylic acid, and the mixture is stirred at about 80° C. (about 24h). The conversion is monitored via the decrease in the carboxylic acidconcentration by means of acid titration, and the epoxide conversion bymeans of Raman spectroscopy/epoxide titration. The band characteristicof the epoxide group is detected in the Raman spectrum at 1256 cm⁻¹. Theepoxide and carboxylic acid conversions are 99% and 88% respectively(consequence of the carboxylic acid excess). 300 mL of ethyl acetate areadded. This is followed by extractive shaking with 2N NaOH solution,washing with water and drying of the organic phase over magnesiumsulfate. After addition of BHT, the solvent is removed under reducedpressure. This results in a mobile resin having a viscosity of 0.3 Pa*sat 25° C.

n_(D) ²⁰=1.466

Light-Curing Polysiloxane/Disiloxane Resins Examples 1-4

CQ and DABE were dissolved in the respective monomers (polysiloxane anddisiloxane). The solutions were freed of air at vacuum −0.9 bar. Theflexural strength (FS) of the individual resins was determined, andthese measurements were used to calculate the modulus of elasticity(MOE).

Surprisingly, a higher modulus of elasticity is found for the mixturesof polysiloxane and disiloxane than for the two respective individualcomponents (FIG. 1). The maximum for the modulus of elasticity was foundat a ratio of polysiloxane to disiloxane of about 2:1.

Example 1

TABLE 1 Composition and properties of poly-/disiloxane resins 1 1-A 1-B1-C 1-D 1-E Polysiloxane 99.25 82.71 66.17 49.625 0.00 I Disiloxane I0.00 16.54 33.08 49.625 99.25 CQ 0.30 0.30 0.30 0.30 0.30 DABE 0.45 0.450.45 0.45 0.45 FS  9.9 MPa 20.8 MPa   25.2 MPa  28.2 MPa 36.3 MPa  MOE560 MPa 960 MPa 1040 MPa 1020 MPa 880 MPa

Example 2

TABLE 2 Composition and properties of poly-/disiloxane resins 2 2-A 2-B2-C 2-D 2-E Polysiloxane 99.25 82.71 66.17 49.625 0.00 II Disiloxane I0.00 16.54 33.08 49.625 99.25 CQ 0.30 0.30 0.30 0.30 0.30 DABE 0.45 0.450.45 0.45 0.45 FS 13.0 MPa   22.3 MPa  23.0 MPa  27.8 MPa 36.3 MPa  MOE920 MPa 1140 MPa 1200 MPa 1130 MPa 880 MPa

Example 3

TABLE 3 Composition and properties of poly-/disiloxane resins 3 3-A 3-B3-C 3-D 3-E Polysiloxane 99.25 82.71 66.17 49.625 0.00 III Disiloxane I0.00 16.54 33.08 49.625 99.25 CQ 0.30 0.30 0.30 0.30 0.30 DABE 0.45 0.450.45 0.45 0.45 FS  19.6 MPa  31.3 MPa  32.0 MPa  31.7 MPa 36.3 MPa  MOE1050 MPa 1360 MPa 1380 MPa 1250 MPa 880 MPa

Example 4

TABLE 4 Composition and properties of poly-/disiloxane resins 4 4-A 4-B4-C 4-D 4-E Polysiloxane 99.25 82.71 66.17 49.625 0.00 IV Disiloxane II0.00 16.54 33.08 49.625 99.25 CQ 0.30 0.30 0.30 0.30 0.30 DABE 0.45 0.450.45 0.45 0.45 FS  25.7 MPa  36.3 MPa  38.1 MPa  34.5 MPa  28.4 MPa MOE1260 MPa 1530 MPa 1550 MPa 1470 MPa 1090 MPa

Production and Properties of Flowable Composite Materials Example 5

For the production of flowable composite pastes, the constituents wereeach weighed out, homogenized in a SpeedMixer™ DAC 600.1 VAC-P(Hauschild & Co. KG, Hamm, Germany), rolled in a three-roll mill (Exakt,Norderstedt, Germany) and then freed of air in the SpeedMixer™ DAC 600.1VAC-P at vacuum −0.9 bar. The viscosity and spreadability of theindividual pastes were measured.

The pastes were dispensed into 1 mL syringes (black, 3-part, Luer lock,with silicone O-ring) from Transcodent GmbH & Co. KG. For thedetermination of Push-out characteristics and push-out force, cannulas(41 type, VOCO GmbH) were used.

TABLE 5 Compositions of the flowable composites 5-B 5-C 5-D 5-E 5-A(comp.) (comp.) (comp.) (comp.) Polysiloxane IV 20.00 35.00 0.00 40.0045.00 Disiloxane I 10.00 0.00 20.00 0.00 0.00 Barium silicate 57.4053.40 62.40 47.90 42.40 glass (1.5 μm) silanized Barium silicate 9.008.00 14.00 6.00 4.00 glass (0.7 μm) silanized Aerosil R8200 2.50 2.502.50 5.00 7.50 CQ 0.40 0.40 0.40 0.40 0.40 DABE 0.60 0.60 0.60 0.60 0.60BHT 0.10 0.10 0.10 0.10 0.10 5-F 5-H 5-I (comp.) 5-G (comp.) (comp.) 5-JPolysiloxane IV 32.00 15.00 6.00 0.00 30.00 Disiloxane I 0.00 7.50 3.0010.00 15.00 Bis-GMA 0.00 5.00 16.00 10.00 0.00 TEGDMA 0.00 2.50 8.0010.00 0.00 Barium silicate 56.40 57.40 54.40 57.40 31.40 glass (1.5 μm)silanized Barium silicate 8.00 9.00 9.00 9.00 20.00 glass (0.7 μm)silanized Aerosil R8200 2.50 2.50 2.50 2.50 2.50 CQ 0.40 0.40 0.40 0.400.40 DABE 0.60 0.60 0.60 0.60 0.60 BHT 0.10 0.10 0.10 0.10 0.10 5-K 5-L5-M 5-N 5-O Polysiloxane IV 20.00 18.00 16.00 16.00 15.00 Disiloxane I10.00 9.00 8.00 0.00 7.50 Disiloxane II 0.00 0.00 0.00 8.00 0.00 Bis-GMA0.00 0.00 0.00 0.00 5.00 TEGDMA 0.00 0.00 0.00 0.00 2.50 Barium silicate51.40 53.40 49.40 49.40 51.40 glass (1.5 μm) silanized Barium silicate7.00 8.00 7.00 7.00 7.00 glass (0.7 μm) silanized Nanoscale SiO₂ 8.008.00 16.00 16.00 8.00 (40 nm) silanized Aerosil R8200 2.50 2.50 2.502.50 2.50 CQ 0.40 0.40 0.40 0.40 0.40 DABE 0.60 0.60 0.60 0.60 0.60 BHT0.10 0.10 0.10 0.10 0.10

TABLE 6 Properties of the flowable composites 5-A 5-B 5-C 5-D 5-E FS 110MPa 94 MPa 75 MPa 82 MPa 71 MPa MOE 6.0 GPa 5.5 GPa 5.0 GPa 5.0 GPa 4.5GPa Shrinkage 2.5% 1.8% 3.5% 2.4% 3.1% Viscosity 10.0 kPa*s 0.8 kPa*s6.5 kPa*s 2.6 kPa*s 7.2 kPa*s (0.01/s) Viscosity 49 Pa*s 53 Pa*s 48 Pa*s61 Pa*s 68 Pa*s (10/s) Push-out good difficult good difficult acceptablecharacteristics Push-out force 33 N 112 N 40 N 101 N 79 N Spreadability61 mm 35 mm 31 mm 38 mm 40 mm 5-F 5-G 5-H 5-I 5-J FS 118 MPa 115 MPa 118MPa 110 MPa 91 MPa MOE 7.6 GPa 7.0 GPa 7.2 GPa 6.5 GPa 5.1 GPa Shrinkage1.6% 3.1% 4.0% 3.6% 3.4% Viscosity 11.6 kPa*s 11.4 kPa*s 9.5 kPa*s 7.8kPa*s 6.8 kPa*s (0.01/s) Viscosity 370 Pa*s 58 Pa*s 55 Pa*s 51 Pa*s 43Pa*s (10/s) Push-out very good good good very characteristics difficultgood Push-out force 189 N 45 N 42 N 30 N 25 N Spreadability 24 mm 51 mm57 mm 55 mm 67 mm 5-K 5-L 5-M 5-N 5-O FS 113 MPa 116 MPa 121 MPa 125 MPa118 MPa MOE 6.5 GPa 6.9 GPa 7.3 GPa 7.5 GPa 7.2 GPa Shrinkage 2.4% 2.2%2.1% 2.0% 3.1% Viscosity 10.8 kPa*s 11.4 kPa*s 11.9 kPa*s 11.8 kPa*s12.1 kPa*s (0.01/s) Viscosity 51 Pa*s 59 Pa*s 63 Pa*s 62 Pa*s 61 Pa*s(10/s) Push-out good good acceptable acceptable good characteristicsPush-out force 41 N 55 N 81 N 79 N 55 N Spreadability 55 mm 51 mm 48 mm47 mm 49 mm

The results show clearly that combination of polysiloxanes anddisiloxanes distinctly improves the properties of the flow material. Asalready found on consideration of the poly-/disiloxane resin mixtures,synergistic effects also occur in the composite. If the different pastesare adjusted to a comparable processible viscosity (at 10 s⁻¹) (5-A toC), it is found that, as well as the expected pure dilution effect oncombination of the specific low-viscosity disiloxane with thehigh-viscosity polysiloxane, unexpectedly better results are achievedwith regard to strength and elasticity properties compared to the pastescomprising either only polysiloxane (5-B) or only disiloxane (5-C).

The better strength properties cannot be explained by a higher fillercontent, since paste 5-C based on the disiloxane, in spite of theincreased solids content, has a lower strength. The crosslinkingproperties of the disiloxane cannot be cited as a reason either, since,as shown by the studies on the resins, they actually have a highercrosslinking potential.

FIG. 2 shows the curves for the viscosity as a function of shear ratefor the inventive flowable material 5-A and of the two comparativematerials 5-B and 5-F. Flowable material 5-A has the viscosity curvetypical of a flowable composite. In the case of a high shear rate, theviscosity is low and the flowable material can flow readily through thecannula. In the case of a low shear rate, the viscosity is high and thematerial is stable.

In the case of 5-B, the viscosity is set so as to correspondapproximately to example 5-A at a shear rate of 10 s⁻¹. On the otherhand, the viscosity at 0.01 s⁻¹ is much lower and the material iscorrespondingly less stable. In the case of 5-F, the viscosity is set soas to correspond approximately to example 5-A at a shear rate of 0.01s⁻¹. On the other hand, the viscosity at 10 s⁻¹ is much higher and thematerial can be pushed-out only with very great difficulty.

If, proceeding from the pure polysiloxane material 5-B, the aerosilcontent is increased (5-D and E), the shear gradient increases asexpected, the viscosity gradually approaches 5-A and the push-outcharacteristics improve (FIG. 3). At the same time, however, theachievable filler content decreases and hence flexural strength andshrinkage deteriorate.

Production and Properties of Core Buildup Materials Example 6

For the production of the base and catalyst pastes of the core buildupmaterials, the constituents were each weighed out, homogenized in aSpeedMixer™ DAC 600.1 VAC-P (Hauschild & Co. KG, Hamm, Germany), rolledin a three-roll mill (Exakt, Norderstedt, Germany) and then freed of airin the SpeedMixer™ DAC 600.1 VAC-P at vacuum −0.9 bar. The viscosity andspreadability of the individual pastes were measured.

The core buildup materials were dispensed into double-chamber syringes(5 mL, 1:1, SDL X05-01-52, PED X05-01-SI) from Sulzer Mixpac AG (Haag,Switzerland). For mixing, the appropriate static mixers ML 2.5-08-D andIOT 212-20 from Sulzer Mixpac AG were attached to the syringes and thetwo components were pushed-out and mixed homogeneously with a plunger(PLH X05-01-46).

TABLE 7 Compositions of the core buildup materials 6-B 6-C 6-D 6-E 6-A(comp.) (comp.) (comp.) (comp.) Base paste Polysiloxane IV 20.00 30.0040.00 0.00 0.00 Disiloxane I 10.00 0.00 0.00 30.00 20.00 Bis-GMA 0.000.00 0.00 0.00 0.00 TEGDMA 0.00 0.00 0.00 0.00 0.00 Barium silicateglass 55.95 55.95 47.95 55.95 63.95 (3.5 μm) silanized Barium silicateglass 10.00 10.00 8.00 10.00 12.00 (0.7 μm) silanized Nanoscale SiO₂ (40Nm) 0.00 0.00 0.00 0.00 0.00 silanized Aerosil R8200 3.00 3.00 3.00 3.003.00 DEPT 0.60 0.60 0.60 0.60 0.60 CQ 0.18 0.18 0.18 0.18 0.18 DABE 0.270.27 0.27 0.27 0.27 Catalyst paste Polysiloxane IV 20.00 30.00 40.000.00 0.00 Disiloxane I 10.00 0.00 0.00 30.00 20.00 Bis-GMA 0.00 0.000.00 0.00 0.00 TEGDMA 0.00 0.00 0.00 0.00 0.00 Barium silicate glass55.95 55.95 47.95 55.95 63.95 (3.5 μm) silanized Barium silicate glass10.00 10.00 8.00 10.00 12.00 (0.7 μm) silanized Nanoscale SiO₂ (40 Nm)0.00 0.00 0.00 0.00 0.00 silanized Aerosil R8200 3.00 3.00 3.00 3.003.00 BPO 1.00 1.00 1.00 1.00 1.00 BHT 0.05 0.05 0.05 0.05 0.05 6-F 6-G6-H 6-I Base paste Polysiloxane IV 16.00 10.00 18.00 16.00 Disiloxane I8.00 5.00 9.00 8.00 Bis-GMA 4.00 10.00 0.00 0.00 TEGDMA 2.00 5.00 0.000.00 Barium silicate glass 55.95 55.95 51.95 47.95 (3.5 μm) silanizedBarium silicate glass 10.00 10.00 8.00 6.00 (0.7 μm) silanized NanoscaleSiO₂ (40 Nm) 0.00 0.00 9.00 18.00 silanized Aerosil R8200 3.00 3.00 3.003.00 DEPT 0.60 0.60 0.60 0.60 CQ 0.18 0.18 0.18 0.18 DABE 0.27 0.27 0.270.27 Catalyst paste Polysiloxane IV 16.00 10.00 18.00 16.00 Disiloxane I8.00 5.00 9.00 8.00 Bis-GMA 4.00 10.00 0.00 0.00 TEGDMA 2.00 5.00 0.000.00 Barium silicate glass 55.95 55.95 51.95 47.95 (3.5 μm) silanizedBarium silicate glass 10.00 10.00 8.00 6.00 (0.7 μm) silanized NanoscaleSiO₂ (40 Nm) 0.00 0.00 9.00 18.00 silanized Aerosil R8200 3.00 3.00 3.003.00 BPO 1.00 1.00 1.00 1.00 BHT 0.05 0.05 0.05 0.05

TABLE 8 Properties of the core buildup materials 6-B 6-C 6-D 6-E 6-A(comp.) (comp.) (comp.) (comp.) FS 108 MPa 115 MPa 97 MPa 75 MPa 85 MPaMOE 7.0 GPa 7.2 GPa 6.2 GPa 5.2 GPa 5.8 GPa Shrinkage 2.6% 1.8% 3.1%4.2% 3.6% Viscosity 8.9 kPa*s 15.1 kPa*s 1.5 kPa*s 5.8 kPa*s 6.7 kPa*s(0.01/s, base) Viscosity 60 Pa*s 105 Pa*s 58 Pa*s 25 Pa*s 68 Pa*s (10/s,base) Viscosity 9.1 kPa*s 15.8 kPa*s 1.6 kPa*s 6.1 kPa*s 6.9 kPa*s(0.01/s, cat.) Viscosity 61 Pa*s 108 Pa*s 60 Pa*s 26 Pa*s 70 Pa*s (10/s,cat.) Push-out good very difficult very good characteristics difficultgood Push-out force 62 N 225 N 121 N 49 N 77 N Spreadability 60 mm 37 mm41 mm 70 mm 49 mm (base) Spreadability 58 mm 36 mm 40 mm 68 mm 48 mm(cat.) 6-F 6-G 6-H 6-I FS 111 MPa 112 MPa 115 MPa 120 MPa MOE 7.1 GPa7.0 GPa 7.3 GPa 7.5 GPa Shrinkage 2.7% 2.8% 2.4% 2.2% Viscosity 9.5kPa*s 9.9 kPa*s 9.8 kPa*s 10.5 kPa*s (0.01/s, base) Viscosity 61 Pa*s 61Pa*s 65 Pa*s 68 Pa*s (10/s, base) Viscosity 9.9 kPa*s 10.2 kPa*s 10.1kPa*s 10.8 kPa*s (0.01/s, cat.) Viscosity 62 Pa*s 63 Pa*s 67 Pa*s 69Pa*s (10/s, cat.) Push-out good good good acceptable characteristicsPush-out force 71 N 76 N 76 N 85 N Spreadability 55 mm 51 mm 54 mm 49 mm(base) Spreadability 53 mm 49 mm 53 mm 48 mm (cat.)

Proceeding from 6-A, in the case of exclusive use of polysiloxane (6-B),flexural strength rises slightly, but the material can still bepushed-out and mixed by means of a static mixer only with very highforce expenditure. If the filler content is lowered (6-C), the materialis still very difficult to push-out and flexural strength decreases.

In the case of exclusive use of disiloxane (6-D), the material has verygood push-out characteristics, but flexural strength is poor. If thefiller content is increased (6-E), flexural strength is still muchpoorer, with comparable push-out characteristics.

Production and Properties of Luting Composites Example 7

For the production of the base and catalyst pastes of the lutingcomposites, the constituents were each weighed out, homogenized in aSpeedMixer™ DAC 600.1 VAC-P (Hauschild & Co. KG, Hamm, Germany), rolledin a three-roll mill (Exakt, Norderstedt, Germany) and then freed of airin the SpeedMixer™ DAC 600.1 VAC-P at vacuum −0.9 bar. The viscosity andspreadability of the individual pastes were measured.

The luting composites were dispensed into double-chamber syringes (5 mL,1:1, SDL X05-01-52, PED X05-01-SI) from Sulzer Mixpac AG (Haag,Switzerland). For mixing, the appropriate static mixers ML 2.5-08-D andIOT 212-20 from Sulzer Mixpac AG were attached to the syringes and thetwo components were pushed-out and mixed homogeneously with a plunger(PLH X05-01-46).

TABLE 9 Compositions of the luting composites 7-A 7-B 7-C 7-D 7-E Basepaste Polysiloxane IV 22.00 22.00 22.00 25.00 18.00 Disiloxane I 11.000.00 11.00 12.50 9.00 Disiloxane II 0.00 11.00 0.00 0.00 0.00 Bariumsilicate glass 43.95 43.95 43.75 36.45 47.95 (1.5 μm) silanized Bariumsilicate glass 20.00 20.00 20.00 22.50 6.00 (0.7 μm) silanized NanoscaleSiO₂ (40 Nm) 0.00 0.00 0.00 0.00 16.00 silanized Aerosil R8200 2.00 2.002.00 2.50 2.00 DEPT 0.60 0.60 0.40 0.60 0.60 NTPB 0.00 0.00 0.40 0.000.00 CQ 0.18 0.18 0.18 0.18 0.18 DABE 0.27 0.27 0.27 0.27 0.27 Catalystpaste Polysiloxane IV 22.00 22.00 18.00 25.00 18.00 Disiloxane I 11.000.00 9.00 12.50 9.00 Disiloxane II 0.00 11.00 0.00 0.00 0.00 MDP 0.000.00 9.00 0.00 0.00 Barium silicate glass 43.95 43.95 40.95 36.45 47.95(1.5 μm) silanized Barium silicate glass 20.00 20.00 20.00 22.50 6.00(0.7 μm) silanized Nanoscale SiO₂ (40 Nm) 0.00 0.00 0.00 0.00 16.00silanized Aerosil R8200 2.00 2.00 2.00 2.50 2.00 BPO 1.00 1.00 1.00 1.001.00 BHT 0.05 0.05 0.05 0.05 0.05

TABLE 10 Properties of the luting composites 7-A 7-B 7-C 7-D 7-E FS 104MPa 113 MPa 102 MPa 91 MPa 119 MPa MOE 6.8 GPa 7.1 GPa 6.5 GPa 6.1 GPa7.6 GPa Shrinkage 2.7% 2.4% 2.7% 3.5% 2.2% Viscosity 8.4 kPa*s 9.6 kPa*s8.8 kPa*s 7.9 kPa*s 10.3 kPa*s (0.1/s, base) Viscosity 55 Pa*s 60 Pa*s56 Pa*s 49 Pa*s 64 Pa*s (10/s, base) Viscosity 8.5 kPa*s 9.9 kPa*s 8.9kPa*s 8.0 kPa*s 10.5 kPa*s (0.1/s, cat.) Viscosity 56 Pa*s 63 Pa*s 60Pa*s 50 Pa*s 65 Pa*s (10/s, cat.) Push-out good good good veryacceptable characteristics good Push-out force 59 N 68 N 69 N 43 N 83 NSpreadability 61 mm 53 mm 59 mm 69 mm 51 mm (base) Spreadability 59 mm51 mm 50 mm 67 mm 50 mm (cat.)

Determination of the Properties:

Flexural strength (FS): The flexural strength is determined inaccordance with ISO 4049. The flowable composites (examples 5) areapplied to the mold from 1 mL syringes (black, 3-part, Luer lock, withsilicone O-ring) from Transcodent GmbH & Co. KG through cannulas (41type, VOCO GmbH). The core buildup and luting composites (examples 6 and7) are applied to the molds from 5 mL double-chamber syringes (SDLX05-01-52, PED X05-01-SI) from Sulzer Mixpac AG (Haag, Switzerland)through a static mixer (ML 2.5-08-D and IOT 212-20). All the materialsare light-cured with a Celalux 2 lamp (VOCO GmbH) section by section for40 seconds. The flexural strength was determined at an advance rate of0.75 mm/min on a Zwick universal tester (Zwick GmbH & Co. KG, Ulm).

Modulus of elasticity (MOE): The modulus of elasticity is determinedfrom the slope in the elastic range of the force-distance curves fromthe flexural strength measurements.

Shrinkage: Shrinkage was determined by the bonded-disk method of Wattset al. (Watts D C, Cash A J, Determination of polymerization kinetics invisible-light cured materials: Methods development, Dent Mater 1991; 7:281-287). A difference was that exposure was effected with a Celalux 2lamp (VOCO GmbH) for 40 seconds per measurement.

Viscosity: The viscosity was determined by means of a rheometer (PhysicaMCR 301) from Anton Paar (Graz, Austria). The measurement is effected at23° C. in a rotation experiment with plate/plate arrangement (diameter25 mm, gap 1 mm) in a shear rate range from 10⁻² to 10 s⁻¹. For eachmeasurement, 16 measured values are recorded within an interval of 30seconds per shear rate. The tables each state the viscosities for theshear rates of 0.01 and 10 s⁻¹. A low shear rate approximatelycorresponds to the viscosity of the material at rest, while high shearrates are observed on application of the material through a narrowcannula or a static mixer.

Push-out characteristics: The flowable composites (examples 5) weredispensed into 1 mL syringes (black, 3-part, Luer lock, with siliconeO-ring) from Transcodent GmbH & Co. KG and pushed-out through cannulas(41 type, VOCO GmbH). The core buildup and luting composites (examples 6and 7) were dispensed into 5 mL double-chamber syringes (SDL X05-01-52,PED X05-01-SI) from Sulzer Mixpac AG (Haag, Switzerland) and pushed-outthrough a static mixer (ML 2.5-08-D and IOT 212-20). Push-outcharacteristics were rated in five levels: very good, good, acceptable,difficult, very difficult.

Push-out force: The flowable composites (examples 5) were dispensed into1 mL syringes (black, 3-part, Luer lock, with silicone O-ring) fromTranscodent GmbH & Co. KG and pushed-out through cannulas (41 type, VOCOGmbH) in a universal tester (Zwick GmbH & Co. KG, Ulm) with an advancerate of 10 mm/min over a distance of 20 mm. The core buildup and lutingcomposites (examples 6 and 7) were dispensed into 5 mL double-chambersyringes (SDL X05-01-52, PED X05-01-SI) from Sulzer Mixpac AG (Haag,Switzerland) and pushed-out through a static mixer (ML 2.5-08-D and IOT212-20) in a universal tester (Zwick GmbH & Co. KG, Ulm) with an advancerate of 23 mm/min over a distance of 30 mm. The respective maximum forcewas evaluated as the push-out force.

Spreadability: The determination of spreadability is effected in aclimate-controlled room at a temperature of 23° C. and a relativehumidity of 50% by means of a glass plate arrangement. The dimensions ofthe plates are 60 mm×60 mm×3 mm, with a plate weight of 25 g. In thedetermination, 0.5 mL of the respective composite paste is applied tothe middle of the first plate. Subsequently, the second plate is placedon cautiously, parallel to the first plate, and a 100 g weight isapplied to the middle. After 10 minutes of weight application, theweight is removed and the greatest and smallest diameters of thecompressed disk of the composite paste are measured. The average of thetwo diameters is reported as the spreadability.

1. A free radically curable dental composition comprising a.) chain-likepolysiloxanes, cyclic polysiloxanes, cage type polysiloxanes, mixedforms thereof, or combinations thereof, wherein the polysiloxanes aresubstituted by free radically polymerizable groups and have at least 3silicon atoms, b.) disiloxanes substituted by free radicallypolymerizable groups and having the following structure:R¹ _(a)R² _((3-a))Si—O—SiR² _((3-b))R¹ _(b) wherein R² is selected fromthe group consisting of alkyl, alkenyl, aryl, alkylaryl, and arylalkyl,wherein different R² may be the same or different, R¹ is YZ, Z is a freeradically polymerizable group selected from the structural elements—O—(C═O)—CH═CH₂, —O—(C═O)—C(CH₃)═CH₂, —(C═O)—CH═CH₂, —(C═O)—C(CH₃)═CH₂,—CH═CH₂, —C(CH₃)═CH₂, —NH—(C═O)—CH═CH₂ and —NH—(C═O)—C(CH₂)═CH₂, whereindifferent Z may be the same or different, a is 1 or 2, b is 1 or 2, Y isa connecting element which links the silicon atom to the free radicallypolymerizable group and consists of an alkylene group, wherein thealkylene group is an unsubstituted, linear, straight chain or branchedhydrocarbyl chain or wherein the alkylene group is an unsubstitutedhydrocarbyl group interrupted by a urethane group, urea group, estergroup, thiourethane group or amide group or wherein the alkylene groupis a hydrocarbyl group substituted by a hydroxyl group or this hydroxylgroup has been esterified or etherified or wherein the alkylene group isa hydrocarbyl group interrupted by an oxygen atom, a nitrogen atom, asulfur atom, ester groups, thioester groups, or combinations thereof andis substituted by a hydroxyl group or this hydroxyl group has beenesterified or etherified, and wherein different Y may be the same ordifferent, and wherein Y contains 20 or fewer carbon atoms, and whereinYZ is chosen such that Z always has a maximum number of atoms, c.)optionally one, two, three or more free radically curable monomershaving no silicon atom, d.) 85 percent by weight or less of one or morefillers based on the total weight of the free radically curable dentalcomposition, e.) initiators, catalysts, or combinations thereof for thefree radical polymerization and f.) further customary additives.
 2. Thedental free radically curable composition as claimed in claim 1, whereinthe polysiloxanes (a.) are obtained by hydrolysis or partial hydrolysisand subsequent condensation or co-condensation of one, two, three ormore compounds R¹ _(a)R² _(b)SiX_(c) wherein X is halogen or alkoxy, R²is selected from the group consisting of alkyl, alkenyl, aryl,alkylaryl, and arylalkyl, wherein different R² may be the same ordifferent, R¹ is YZ, Z is a free radically polymerizable group selectedfrom the structural elements —O—(C═O)—CH═CH₂, —O—(C═O)—C(CH₃)═CH₂,—(C═O)—CH═CH₂, —(C═O)—C(CH₃)═CH₂, —CH═CH₂, —C(CH₃)═CH₂, —NH—(C═O)—CH═CH₂and —NH—(C═O)—C(CH₃)═CH₂, wherein different Z may be the same ordifferent, a is 1 or 2, b is 0 or 1, c is 2 or 3,a+b+c=4, Y is a connecting element which links the silicon atom to thefree radically polymerizable group and consists of an alkylene group,wherein the alkylene group is an unsubstituted, linear, straight chainor branched hydrocarbyl chain or wherein the alkylene group is anunsubstituted hydrocarbyl group interrupted by a urethane group, ureagroup, ester group, thiourethane group or amide group or wherein thealkylene group is a hydrocarbyl group substituted by a hydroxyl group orthis hydroxyl group has been esterified or etherified or wherein thealkylene group is a hydrocarbyl group interrupted by an oxygen atom, anitrogen atom, a sulfur atom, ester groups, thioester groups, orcombinations thereof and is substituted by a hydroxyl group or thishydroxyl group has been esterified or etherified, and wherein differentY may be the same or different, and wherein Y contains 20 or fewercarbon atoms, and wherein YZ is chosen such that Z always has a maximumnumber of atoms.
 3. The free radically curable dental composition asclaimed in claim 1, wherein the composition contains: constituent a.) inan amount of 10%-35% by weight, constituent b.) in an amount of 2%-25%by weight, constituent c.) in an amount of 0%-20% by weight, constituentd.) in an amount of 50%-85% by weight, constituent e.) in an amount of0.001%-5% by weight, constituent f.) in an amount of 0.001%-20% byweight, and wherein the respective percentages by weight are based onthe total mass of the composition.
 4. The free radically curable dentalcomposition as claimed in claim 1, wherein the composition contains, asconstituent b.), 1,3bis(3 methacryloyloxypropyl)tetramethyldisiloxane.5. The free radically curable dental composition as claimed in claim 1,wherein the composition does not contain any constituent c.).
 6. Thefree radically curable dental composition as claimed in claim 1,containing a mixture of fillers d.) comprising: d.1. organically surfacemodified inorganic nanoparticles having an average particle size of lessthan 200 nm, d.2. inorganic microparticles having an average particlesize in the range from 0.4 μm to 10 μm and d.3. optionally furtherfillers which do not correspond to d.1. and d.2.
 7. The free radicallycurable dental composition as claimed in claim 6, wherein component d.1.is at least partly in nonagglomerated or nonaggregated form.
 8. Thefree-radically curable dental composition as claimed in claim 6, whereincomponent d.2. contains two or more micro fractions, wherein a firstmicro fraction or each of a plurality of first micro fractions has anaverage particle size in the range from 1 to 10 μm, and wherein a secondmicroparticle fraction or each of a plurality of second microparticlefractions has an average particle size in the range from greater than0.4 μm to less than 1 μm.
 9. The free-radically curable dentalcomposition as claimed in claim 8, wherein the ratio of the total massof the first microparticle fraction(s) to the total mass of the secondmicroparticle fraction(s) is in the range from 1:1 to 12:1.
 10. Thefree-radically curable dental composition as claimed in claim 8, whereinthe ratio of the average particle size of the first or a firstmicroparticle fraction to the average particle size of the second or asecond microparticle fraction of component d.2. is in the range from1.5:1 to 10:1.
 11. The free-radically curable dental composition asclaimed in claim 6, wherein at least some of the microparticles ofcomponent d.2. are selected from the group consisting of organicallysurface modified particles, dental glass particles, and combinationsthereof, wherein at least some of the microparticles of component d.2.are organically surface modified dental glass particles.
 12. Thefree-radically curable dental composition as claimed in claim 6, whereinthe composition contains: component d.1. in an amount of 1%-20% byweight, component d.2. in an amount of 30%-84% by weight, component d.3.in an amount of 0%-30% by weight, and wherein the percentages by weightare based on the total mass of the free radically curable dentalcomposition.
 13. The free-radically curable dental composition asclaimed in claim 1, wherein constituent d.) contains x ray opaquefractions.
 14. The free-radically curable dental composition as claimedin claim 13, wherein the x ray opaque fractions are nanoscale YbF₃,BaSO₄, or combinations thereof.
 15. The free-radically curable dentalcomposition as claimed in claim 1, wherein the free radicallypolymerizable groups are acrylate or methacrylate groups.
 16. A curedfree-radically curable dental composition produced by the method ofclaim 19, wherein the cured dental composition has a shrinkage of lessthan 3.5% by volume.
 17. (canceled)
 18. A method for producing afree-radically curable composition as claimed in claim 1 comprisingmixing constituents a. to f.
 19. A process for producing a cured dentalcomposition, comprising the following steps: providing a free-radicallycurable dental composition as claimed in claim 1, and polymerizing thefree-radically curable dental composition.
 20. A kit comprising at leastone component selected from the group consisting of a dental syringe, adental compule, a double-chamber cartridge, and combinations thereof,wherein the kit further comprises (i) one, two or more than twofree-radically curable dental compositions as claimed in claim 1, (ii)one, two or more than two base pastes and one, two or more than twocatalyst pastes, wherein a free-radically curable dental material asclaimed in claim 1 is obtainable by mixing a base paste and thecorresponding catalyst paste, or combinations of (i) and (ii). 21.(canceled)
 22. The free radically curable dental composition as claimedin claim 1, wherein the composition contains: constituent a.) in anamount of 15%-25% by weight, constituent b.) in an amount of 5%-15% byweight, constituent c.) in an amount of 0%-10% by weight, constituentd.) in an amount of 60%-78% by weight, constituent e.) in an amount of0.1%-2% by weight and constituent f.) in an amount of 0.001%-10% byweight, and wherein the respective percentages by weight are based onthe total mass of the composition.